Filler, not function. The 36-066 is a trim ring that sits between the lock trim and the face of the door on the Schlage B100, B250, B400, E, B, H, MD and S200 series, closing the gap at the edge of the bore and giving the trim a flat seat. It has no keying, latching or locking role of its own, which is why it gets bought on its own: the original ring went missing during a rekey, got chewed up on removal, or the trim won't sit flush against the door. Size is 1/8 inch.

626 is satin chrome, the same BHMA finish code carried across commercial levers, cylinders and deadbolt trim, so this ring sits next to other 626 hardware without reading as a mismatch. Worth knowing which chrome you actually have on the doors: 626 is the brushed satin tone, not the mirror-bright 625, and it will contrast plainly against brass or bronze trim such as 605 or 613. Ordered as 36-066 626.

Schlage 36-066 626. Both halves of that matter on a purchase order: 36-066 identifies the trim ring and 1/8 inch size, and 626 is the satin chrome finish suffix. Dropping the finish code off the line is the usual way one of these turns up in the wrong plating.