Crosman Crosman 3622 barrel band shim question

[wsjones]

I bought one of these directly from Crosman a couple weeks ago and have almost finished the minor mods on it: steel breech, Airgun Mods moderator, BSA 2-7x32 compact scope.

I've read and heard on videos about shimming the front barrel band to create a slightly wider gap between the tube and barrel to make attaching air hose's female foster fitting easier. My question is just what are people using for the shims?

Thanks. Scott