Create a product which is composed of other products.
Add the following line to your Gemfile
gem "spree_product_assembly", :git => "git://github.com/spree/spree-product-assembly.git"
Run bundle install as well as the extension intall command to copy and run migrations
bundle install
rails g spree_product_assembly:install
Use 1-3-stable branch for Spree 1.3.x compatibility
This extension adds a can_be_part
boolean attribute to the spree_products_table.
You'll need to check that flag on the backend product form so that it can be
be found by the parts searchs form.
Once a product is included as a part of another it will be included on the order shipment with zero costs.