A slim, aluminum tube that provides the optimal grip for holding a bit in a Dremel rotary tool. The collet features small identification rings around its shankThese rings correspond with the size of the collet: 0 rings = 1/8 in., 3 rings = 3/32 in., 2 rings = 1/16 in., 1 ring = 1/32 in.Collets are compatible with 225 flex-shaft attachmentFor use with all rotary tools except discontinued models 1, 2, and series 1 or earlier of discontinued models 260, 270 and 280