Seat Post Shim
Fits frame designed for 27.2mm posts and reduces to 25.4mm post.
30.9 or 31.6 to reduce to 27.2 post so you can put a pivotal seat post in your dirt jumper.
Shim is 3" long and is slotted to allow seat clamp to tighten.
30.9 is a different design from a different manufacturer, its the only one we could get in this size, hence the price difference.