Just been and had a look and can't find it. But I definitely have one, I bought a bike
with one, I still have the frame and seatpost, so assumed the shim was in place it
wasn't.
I will have another look tomorrow.
right so the seapost shims i have are useless to you (31.0 OD ->26.8 ID) & 30.6 OD with unknown ID.
and something else that's useless to you, i sold my USE SX seatpost on ebay a few months ago. i would have gladly karma'd those bits to you.....
sorry to be so slow and ultimately useless.