These are black EPDM rubber silencing washers that are commonly used with TLMAB mounting posts, chicago screws, slotted posts and other 3/16" diameter sheath and holster mounting assemblies. They are used to cushion and silence the contact points between the holster and mounting attachments. EPDM synthetic rubber is a bit more rigid than neoprene and allows less flex between the attachment and the holster/sheath. This is preferred by some custom holster and sheath makers. Specifications
EDPM Synthetic Rubber
Durometer = 60
Color - Black
.500 OD x .180 ID x .480 Thick