This is pair of metal inserts we had made for the LIDO 1 catch cup jar lid, about half way through the LIDO 1 production series (750 grinders). Thick aluminum clam shells reduce the amount of plastic exposure in the catch cup plastic lid, and protect the plastic lid from gouging by the fasteners. We have sometimes referred to this as the "full metal jacket". Installation is pretty obvious, but do one side at a time. Available while supplies last (we have 63 pair on hand as of 10/16/2013)