diff --git a/module/core/reflect_tools/src/reflect/fields.rs b/module/core/reflect_tools/src/reflect/fields.rs
index 428c95237b..edbdfbc9b4 100644
--- a/module/core/reflect_tools/src/reflect/fields.rs
+++ b/module/core/reflect_tools/src/reflect/fields.rs
@@ -112,6 +112,10 @@ mod private
 mod vec;
 mod hmap;
 mod bmap;
+mod hset;
+mod bset;
+mod deque;
+mod llist;
 
 #[ doc( inline ) ]
 #[ allow( unused_imports ) ]
diff --git a/module/core/reflect_tools/src/reflect/fields/bset.rs b/module/core/reflect_tools/src/reflect/fields/bset.rs
new file mode 100644
index 0000000000..e68d4d7e4b
--- /dev/null
+++ b/module/core/reflect_tools/src/reflect/fields/bset.rs
@@ -0,0 +1,65 @@
+//!
+//! Implement fields for BTreeSet.
+//!
+
+use crate::*;
+use std::borrow::Cow;
+use collection_tools::BTreeSet;
+
+impl< V, Borrowed > Fields< usize, &'_ Borrowed > for BTreeSet< V >
+where
+  Borrowed : std::borrow::ToOwned + 'static + ?Sized,
+  V : std::borrow::Borrow< Borrowed >,
+{
+
+  type Key< 'k > = usize
+  where Self : 'k, usize : 'k;
+
+  type Val< 'v > = &'v Borrowed
+  where Self : 'v, V : 'v;
+
+  fn fields< 's >( &'s self ) -> impl IteratorTrait< Item = ( Self::Key< 's >, Self::Val< 's > ) >
+  {
+    self.iter().enumerate().map( move | ( key, val ) | ( key, val.borrow() ) )
+  }
+
+}
+
+impl< V, Borrowed > Fields< usize, Option< Cow< '_, Borrowed > > > for BTreeSet< V >
+where
+  Borrowed : std::borrow::ToOwned + 'static + ?Sized,
+  V : std::borrow::Borrow< Borrowed >,
+{
+
+  type Key< 'k > = usize
+  where Self : 'k, usize : 'k;
+
+  type Val< 'v > = Option< Cow< 'v, Borrowed > >
+  where Self : 'v;
+
+  fn fields< 's >( &'s self ) -> impl IteratorTrait< Item = ( Self::Key< 's >, Self::Val< 's > ) >
+  {
+    self.iter().enumerate().map( move | ( key, val ) | ( key, Some( Cow::Borrowed( val.borrow() ) ) ) )
+  }
+
+}
+
+impl< V, Borrowed, Marker > Fields< usize, OptionalCow< '_, Borrowed, Marker > > for BTreeSet< V >
+where
+  Borrowed : std::borrow::ToOwned + 'static + ?Sized,
+  V : std::borrow::Borrow< Borrowed >,
+  Marker : Clone + Copy + 'static,
+{
+
+  type Key< 'k > = usize
+  where Self : 'k, usize : 'k;
+
+  type Val< 'v > = OptionalCow< 'v, Borrowed, Marker >
+  where Self : 'v;
+
+  fn fields< 's >( &'s self ) -> impl IteratorTrait< Item = ( Self::Key< 's >, Self::Val< 's > ) >
+  {
+    self.iter().enumerate().map( move | ( key, val ) | ( key, OptionalCow::from( val.borrow() ) ) )
+  }
+
+}
diff --git a/module/core/reflect_tools/src/reflect/fields/deque.rs b/module/core/reflect_tools/src/reflect/fields/deque.rs
new file mode 100644
index 0000000000..734255ad1a
--- /dev/null
+++ b/module/core/reflect_tools/src/reflect/fields/deque.rs
@@ -0,0 +1,65 @@
+//!
+//! Implement fields for Deque.
+//!
+
+use crate::*;
+use std::borrow::Cow;
+use collection_tools::VecDeque;
+
+impl< V, Borrowed > Fields< usize, &'_ Borrowed > for VecDeque< V >
+where
+  Borrowed : std::borrow::ToOwned + 'static + ?Sized,
+  V : std::borrow::Borrow< Borrowed >,
+{
+
+  type Key< 'k > = usize
+  where Self : 'k, usize : 'k;
+
+  type Val< 'v > = &'v Borrowed
+  where Self : 'v, V : 'v;
+
+  fn fields< 's >( &'s self ) -> impl IteratorTrait< Item = ( Self::Key< 's >, Self::Val< 's > ) >
+  {
+    self.iter().enumerate().map( move | ( key, val ) | ( key, val.borrow() ) )
+  }
+
+}
+
+impl< V, Borrowed > Fields< usize, Option< Cow< '_, Borrowed > > > for VecDeque< V >
+where
+  Borrowed : std::borrow::ToOwned + 'static + ?Sized,
+  V : std::borrow::Borrow< Borrowed >,
+{
+
+  type Key< 'k > = usize
+  where Self : 'k, usize : 'k;
+
+  type Val< 'v > = Option< Cow< 'v, Borrowed > >
+  where Self : 'v;
+
+  fn fields< 's >( &'s self ) -> impl IteratorTrait< Item = ( Self::Key< 's >, Self::Val< 's > ) >
+  {
+    self.iter().enumerate().map( move | ( key, val ) | ( key, Some( Cow::Borrowed( val.borrow() ) ) ) )
+  }
+
+}
+
+impl< V, Borrowed, Marker > Fields< usize, OptionalCow< '_, Borrowed, Marker > > for VecDeque< V >
+where
+  Borrowed : std::borrow::ToOwned + 'static + ?Sized,
+  V : std::borrow::Borrow< Borrowed >,
+  Marker : Clone + Copy + 'static,
+{
+
+  type Key< 'k > = usize
+  where Self : 'k, usize : 'k;
+
+  type Val< 'v > = OptionalCow< 'v, Borrowed, Marker >
+  where Self : 'v;
+
+  fn fields< 's >( &'s self ) -> impl IteratorTrait< Item = ( Self::Key< 's >, Self::Val< 's > ) >
+  {
+    self.iter().enumerate().map( move | ( key, val ) | ( key, OptionalCow::from( val.borrow() ) ) )
+  }
+
+}
diff --git a/module/core/reflect_tools/src/reflect/fields/hset.rs b/module/core/reflect_tools/src/reflect/fields/hset.rs
new file mode 100644
index 0000000000..cfc01be06e
--- /dev/null
+++ b/module/core/reflect_tools/src/reflect/fields/hset.rs
@@ -0,0 +1,65 @@
+//!
+//! Implement fields for HashSet.
+//!
+
+use crate::*;
+use std::borrow::Cow;
+use std::collections::HashSet;
+
+impl< V, Borrowed > Fields< usize, &'_ Borrowed > for HashSet< V >
+where
+  Borrowed : std::borrow::ToOwned + 'static + ?Sized,
+  V : std::borrow::Borrow< Borrowed >,
+{
+
+  type Key< 'k > = usize
+  where Self : 'k, usize : 'k;
+
+  type Val< 'v > = &'v Borrowed
+  where Self : 'v, V : 'v;
+
+  fn fields< 's >( &'s self ) -> impl IteratorTrait< Item = ( Self::Key< 's >, Self::Val< 's > ) >
+  {
+    self.iter().enumerate().map( move | ( key, val ) | ( key, val.borrow() ) )
+  }
+
+}
+
+impl< V, Borrowed > Fields< usize, Option< Cow< '_, Borrowed > > > for HashSet< V >
+where
+  Borrowed : std::borrow::ToOwned + 'static + ?Sized,
+  V : std::borrow::Borrow< Borrowed >,
+{
+
+  type Key< 'k > = usize
+  where Self : 'k, usize : 'k;
+
+  type Val< 'v > = Option< Cow< 'v, Borrowed > >
+  where Self : 'v;
+
+  fn fields< 's >( &'s self ) -> impl IteratorTrait< Item = ( Self::Key< 's >, Self::Val< 's > ) >
+  {
+    self.iter().enumerate().map( move | ( key, val ) | ( key, Some( Cow::Borrowed( val.borrow() ) ) ) )
+  }
+
+}
+
+impl< V, Borrowed, Marker > Fields< usize, OptionalCow< '_, Borrowed, Marker > > for HashSet< V >
+where
+  Borrowed : std::borrow::ToOwned + 'static + ?Sized,
+  V : std::borrow::Borrow< Borrowed >,
+  Marker : Clone + Copy + 'static,
+{
+
+  type Key< 'k > = usize
+  where Self : 'k, usize : 'k;
+
+  type Val< 'v > = OptionalCow< 'v, Borrowed, Marker >
+  where Self : 'v;
+
+  fn fields< 's >( &'s self ) -> impl IteratorTrait< Item = ( Self::Key< 's >, Self::Val< 's > ) >
+  {
+    self.iter().enumerate().map( move | ( key, val ) | ( key, OptionalCow::from( val.borrow() ) ) )
+  }
+
+}
diff --git a/module/core/reflect_tools/src/reflect/fields/llist.rs b/module/core/reflect_tools/src/reflect/fields/llist.rs
new file mode 100644
index 0000000000..40ca1ced98
--- /dev/null
+++ b/module/core/reflect_tools/src/reflect/fields/llist.rs
@@ -0,0 +1,65 @@
+//!
+//! Implement fields for LinkedList.
+//!
+
+use crate::*;
+use std::borrow::Cow;
+use collection_tools::LinkedList;
+
+impl< V, Borrowed > Fields< usize, &'_ Borrowed > for LinkedList< V >
+where
+  Borrowed : std::borrow::ToOwned + 'static + ?Sized,
+  V : std::borrow::Borrow< Borrowed >,
+{
+
+  type Key< 'k > = usize
+  where Self : 'k, usize : 'k;
+
+  type Val< 'v > = &'v Borrowed
+  where Self : 'v, V : 'v;
+
+  fn fields< 's >( &'s self ) -> impl IteratorTrait< Item = ( Self::Key< 's >, Self::Val< 's > ) >
+  {
+    self.iter().enumerate().map( move | ( key, val ) | ( key, val.borrow() ) )
+  }
+
+}
+
+impl< V, Borrowed > Fields< usize, Option< Cow< '_, Borrowed > > > for LinkedList< V >
+where
+  Borrowed : std::borrow::ToOwned + 'static + ?Sized,
+  V : std::borrow::Borrow< Borrowed >,
+{
+
+  type Key< 'k > = usize
+  where Self : 'k, usize : 'k;
+
+  type Val< 'v > = Option< Cow< 'v, Borrowed > >
+  where Self : 'v;
+
+  fn fields< 's >( &'s self ) -> impl IteratorTrait< Item = ( Self::Key< 's >, Self::Val< 's > ) >
+  {
+    self.iter().enumerate().map( move | ( key, val ) | ( key, Some( Cow::Borrowed( val.borrow() ) ) ) )
+  }
+
+}
+
+impl< V, Borrowed, Marker > Fields< usize, OptionalCow< '_, Borrowed, Marker > > for LinkedList< V >
+where
+  Borrowed : std::borrow::ToOwned + 'static + ?Sized,
+  V : std::borrow::Borrow< Borrowed >,
+  Marker : Clone + Copy + 'static,
+{
+
+  type Key< 'k > = usize
+  where Self : 'k, usize : 'k;
+
+  type Val< 'v > = OptionalCow< 'v, Borrowed, Marker >
+  where Self : 'v;
+
+  fn fields< 's >( &'s self ) -> impl IteratorTrait< Item = ( Self::Key< 's >, Self::Val< 's > ) >
+  {
+    self.iter().enumerate().map( move | ( key, val ) | ( key, OptionalCow::from( val.borrow() ) ) )
+  }
+
+}
diff --git a/module/core/reflect_tools/tests/inc/fundamental/fields_bset.rs b/module/core/reflect_tools/tests/inc/fundamental/fields_bset.rs
new file mode 100644
index 0000000000..5a811ad569
--- /dev/null
+++ b/module/core/reflect_tools/tests/inc/fundamental/fields_bset.rs
@@ -0,0 +1,61 @@
+#[ allow( unused_imports ) ]
+use super::*;
+
+use the_module::
+{
+  Fields,
+
+};
+
+// xxx : implement for other collections
+
+use std::
+{
+  borrow::Cow,
+};
+
+#[ test ]
+fn bset_string_fields()
+{
+  let collection : BTreeSet< String >  = bset!
+  [
+    "a".to_string(),
+    "b".to_string(),
+  ];
+
+  // k, v
+  let got : BTreeSet< _ > = Fields::< usize, &str >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  let exp = bset![ ( 0, "a" ), ( 1, "b" ) ];
+  assert_eq!( got, exp );
+
+  // k, Option< Cow< '_, str > >
+  let got : BTreeSet< _ > = Fields::< usize, Option< Cow< '_, str > > >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  let exp = bset![ ( 0, Some( Cow::Borrowed( "a" ) ) ), ( 1, Some( Cow::Borrowed( "b" ) ) ) ];
+  assert_eq!( got, exp );
+
+}
+
+#[ test ]
+fn bset_str_fields()
+{
+  let collection : BTreeSet< &str > = bset!
+  [
+    "a",
+    "b",
+  ];
+
+  // k, v
+  let got : BTreeSet< _ > = Fields::< usize, &str >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  let exp = bset![ ( 0, "a" ), ( 1, "b" ) ];
+  assert_eq!( got, exp );
+
+  // k, Option< Cow< '_, str > >
+  let got : BTreeSet< _ > = Fields::< usize, Option< Cow< '_, str > > >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  let exp = bset![ ( 0, Some( Cow::Borrowed( "a" ) ) ), ( 1, Some( Cow::Borrowed( "b" ) ) ) ];
+  assert_eq!( got, exp );
+
+}
diff --git a/module/core/reflect_tools/tests/inc/fundamental/fields_deque.rs b/module/core/reflect_tools/tests/inc/fundamental/fields_deque.rs
new file mode 100644
index 0000000000..190d8fc57b
--- /dev/null
+++ b/module/core/reflect_tools/tests/inc/fundamental/fields_deque.rs
@@ -0,0 +1,73 @@
+#[ allow( unused_imports ) ]
+use super::*;
+
+use the_module::
+{
+  Fields,
+  OptionalCow,
+};
+
+// xxx : implement for other collections
+
+use std::
+{
+  borrow::Cow,
+};
+
+#[ test ]
+fn deque_string_fields()
+{
+  let collection = deque!
+  [
+    "a".to_string(),
+    "b".to_string(),
+  ];
+
+  // k, v
+  let got : VecDeque< _ > = Fields::< usize, &str >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  let exp = deque![ ( 0, "a" ), ( 1, "b" ) ];
+  assert_eq!( got, exp );
+
+  // k, Option< Cow< '_, str > >
+  let got : VecDeque< _ > = Fields::< usize, Option< Cow< '_, str > > >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  let exp = deque![ ( 0, Some( Cow::Borrowed( "a" ) ) ), ( 1, Some( Cow::Borrowed( "b" ) ) ) ];
+  assert_eq!( got, exp );
+
+  // k, OptionalCow< '_, str, () >
+  let got : VecDeque< _ > = Fields::< usize, OptionalCow< '_, str, () > >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  let exp = deque![ ( 0, OptionalCow::from( "a" ) ), ( 1, OptionalCow::from( "b" ) ) ];
+  assert_eq!( got, exp );
+
+}
+
+#[ test ]
+fn deque_str_fields()
+{
+  let collection = deque!
+  [
+    "a",
+    "b",
+  ];
+
+  // k, v
+  let got : VecDeque< _ > = Fields::< usize, &str >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  let exp = deque![ ( 0, "a" ), ( 1, "b" ) ];
+  assert_eq!( got, exp );
+
+  // k, Option< Cow< '_, str > >
+  let got : VecDeque< _ > = Fields::< usize, Option< Cow< '_, str > > >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  let exp = deque![ ( 0, Some( Cow::Borrowed( "a" ) ) ), ( 1, Some( Cow::Borrowed( "b" ) ) ) ];
+  assert_eq!( got, exp );
+
+  // k, OptionalCow< '_, str, () >
+  let got : VecDeque< _ > = Fields::< usize, OptionalCow< '_, str, () > >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  let exp = deque![ ( 0, OptionalCow::from( "a" ) ), ( 1, OptionalCow::from( "b" ) ) ];
+  assert_eq!( got, exp );
+
+}
diff --git a/module/core/reflect_tools/tests/inc/fundamental/fields_hset.rs b/module/core/reflect_tools/tests/inc/fundamental/fields_hset.rs
new file mode 100644
index 0000000000..fddc44dc94
--- /dev/null
+++ b/module/core/reflect_tools/tests/inc/fundamental/fields_hset.rs
@@ -0,0 +1,60 @@
+#[ allow( unused_imports ) ]
+use super::*;
+
+use the_module::
+{
+  Fields,
+};
+
+// xxx : implement for other collections
+
+use std::
+{
+  borrow::Cow,
+};
+
+#[ test ]
+fn hset_string_fields()
+{
+  let collection : HashSet< String > = hset!
+  [
+    "a".to_string(),
+    "b".to_string(),
+  ];
+
+  // k, v
+  let got : HashSet< _ > = Fields::< usize, &str >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  assert!( got.contains(&( 0, "a" ) ) || got.contains(&( 1, "a" ) ) );
+  assert!( got.contains(&( 0, "b" ) ) || got.contains(&( 1, "b" ) ) );
+
+  // k, Option< Cow< '_, str > >
+  let got : HashSet< _ > = Fields::< usize, Option< Cow< '_, str > > >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  assert!( got.contains(&( 0, Some( Cow::Borrowed( "a" ) ) ) ) || got.contains(&( 1, Some( Cow::Borrowed( "a" ) ) ) ) );
+  assert!( got.contains(&( 0, Some( Cow::Borrowed( "b" ) ) ) ) || got.contains(&( 1, Some( Cow::Borrowed( "b" ) ) ) ) );
+
+}
+
+#[ test ]
+fn hset_str_fields()
+{
+  let collection : HashSet< &str > = hset!
+  [
+    "a",
+    "b",
+  ];
+
+  // k, v
+  let got : HashSet< _ > = Fields::< usize, &str >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  assert!( got.contains(&( 0, "a" ) ) || got.contains(&( 1, "a" ) ) );
+  assert!( got.contains(&( 0, "b" ) ) || got.contains(&( 1, "b" ) ) );
+
+  // k, Option< Cow< '_, str > >
+  let got : HashSet< _ > = Fields::< usize, Option< Cow< '_, str > > >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  assert!( got.contains(&( 0, Some( Cow::Borrowed( "a" ) ) ) ) || got.contains(&( 1, Some( Cow::Borrowed( "a" ) ) ) ) );
+  assert!( got.contains(&( 0, Some( Cow::Borrowed( "b" ) ) ) ) || got.contains(&( 1, Some( Cow::Borrowed( "b" ) ) ) ) );
+
+}
diff --git a/module/core/reflect_tools/tests/inc/fundamental/fields_llist.rs b/module/core/reflect_tools/tests/inc/fundamental/fields_llist.rs
new file mode 100644
index 0000000000..dc93d87c0a
--- /dev/null
+++ b/module/core/reflect_tools/tests/inc/fundamental/fields_llist.rs
@@ -0,0 +1,73 @@
+#[ allow( unused_imports ) ]
+use super::*;
+
+use the_module::
+{
+  Fields,
+  OptionalCow,
+};
+
+// xxx : implement for other collections
+
+use std::
+{
+  borrow::Cow,
+};
+
+#[ test ]
+fn llist_string_fields()
+{
+  let collection = llist!
+  [
+    "a".to_string(),
+    "b".to_string(),
+  ];
+
+  // k, v
+  let got : LinkedList< _ > = Fields::< usize, &str >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  let exp = llist![ ( 0, "a" ), ( 1, "b" ) ];
+  assert_eq!( got, exp );
+
+  // k, Option< Cow< '_, str > >
+  let got : LinkedList< _ > = Fields::< usize, Option< Cow< '_, str > > >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  let exp = llist![ ( 0, Some( Cow::Borrowed( "a" ) ) ), ( 1, Some( Cow::Borrowed( "b" ) ) ) ];
+  assert_eq!( got, exp );
+
+  // k, OptionalCow< '_, str, () >
+  let got : LinkedList< _ > = Fields::< usize, OptionalCow< '_, str, () > >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  let exp = llist![ ( 0, OptionalCow::from( "a" ) ), ( 1, OptionalCow::from( "b" ) ) ];
+  assert_eq!( got, exp );
+
+}
+
+#[ test ]
+fn llist_str_fields()
+{
+  let collection = llist!
+  [
+    "a",
+    "b",
+  ];
+
+  // k, v
+  let got : LinkedList< _ > = Fields::< usize, &str >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  let exp = llist![ ( 0, "a" ), ( 1, "b" ) ];
+  assert_eq!( got, exp );
+
+  // k, Option< Cow< '_, str > >
+  let got : LinkedList< _ > = Fields::< usize, Option< Cow< '_, str > > >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  let exp = llist![ ( 0, Some( Cow::Borrowed( "a" ) ) ), ( 1, Some( Cow::Borrowed( "b" ) ) ) ];
+  assert_eq!( got, exp );
+
+  // k, OptionalCow< '_, str, () >
+  let got : LinkedList< _ > = Fields::< usize, OptionalCow< '_, str, () > >::fields( &collection ).collect();
+  assert_eq!( got.len(), 2 );
+  let exp = llist![ ( 0, OptionalCow::from( "a" ) ), ( 1, OptionalCow::from( "b" ) ) ];
+  assert_eq!( got, exp );
+
+}
diff --git a/module/core/reflect_tools/tests/inc/mod.rs b/module/core/reflect_tools/tests/inc/mod.rs
index de4b0b494e..d0ec8fff41 100644
--- a/module/core/reflect_tools/tests/inc/mod.rs
+++ b/module/core/reflect_tools/tests/inc/mod.rs
@@ -12,6 +12,10 @@ mod fundamental
   mod fields_vec;
   mod fields_hmap;
   mod fields_bmap;
+  mod fields_bset;
+  mod fields_deque;
+  mod fields_hset;
+  mod fields_llist;
 
 }