Catch weight
If an item is ordered in a different unit of measure (UOM) than the
UOM in which you sell or dispense the item, then use catch weight.
The price that you pay when you purchase the item is based on weight, but the weight per each unit may vary.
For example, you can buy cheese by the block at the grocery store but you pay for it by the pound. The unit is essentially delivered by a description and priced by weight.