This is a NEW seatpost shim.  If It is used to make your seatpost fit into your oversized seat tube.  It's really simpleFor example: If You have a 27.2mm seatpost (suspension or standard), but you have a frame with a 31.6 mm ID seat tube.  You put this shim/spacer in your seat tube and voila!  Your 27.2mm seatpost will fit precisely in your 31.6mm ID seat tube.

Wondering what size seat tube ID you have?  Often your old seatpost will have it stamped on it, near the bottom. 

Features:
* ID is 27.2mm, thickness is 4.2 mm, OD is 31.6mm
* Fits 27.2mm seatposts and 31.6 mm ID seat tubes (your frame)
* 90mm long
* Color:  Black
* 6061 Aluminum
* Anodized finish
* Size info printed right on shim
                              Please choose the correct size you need according to the type. Thank you very much.