On the BOM components list, I need to have a different Unit of Measure from the Stock UOM.

The Item Master has the Stock UOM as KG (This is steel plate).  In the customer's new CAD they want to define the cut size (or length) of component.

In this case, they want to specify 3 pieces to be cut 250mm x 300mm.  let's say that this equates to 1.8 KG of the steel plate.

I can put a description in Link Description field saying cut 3 plate 250.300mm, but the customer wants to have 3 pieces 250x300mm

I have tried Pack units on the component item master, but the BOM wont allow the UOM as it's not a Volume/Weight UOM.

Any ideas?