Lot control allows you to trace the origin of inventory that eventually you'll use in project builds. Essentially, whenever you receive parts against a purchase order or you finish a project build, the resulting inventory can be assigned a Lot. That way, when using inventory from a Lot in a project build you will be able to tell from where and how you sourced it. This can be especially useful to troubleshoot faulty production units. Lot control is available on professional plans.