The VeloBase.com Parts Bin is a collection of all Components and Frame Parts which have been specified as part of a bicycle, but has not been added to the Component or Frame Parts collection. For instance, a particular Regina freewheel was the original spec on a Colnago Masterlight which was recently added to the Bicycle collection. However the exact match for this component did not exist in the database. An item is created in the Parts Bin when the Colnago is added. Kind of a place holder for when the correct Regina part is added to the database. And when it is, the Colnago's listing is automatically updated to reference the complete Component listing instead of the item in the Parts Bin.
If you have add/edit permissions here on VeloBase.com, you can click on any of the items in the Parts Bin to update, merge, or create a complete VeloBase Component / Frame Part from it.