Originally Posted by
ZManT
it was packaged together with the plug - wrapped up in plastic and taped to the fork.
it was less than 1 mm thick, so i doubt it was the shim you speak of - silver aluminum, textured coating - looked like something to help the expansion plug "bite" - but I'll be damned if I could figure out how to use it with my fork ....
Maybe your original guess was correct that it's there to allow the plug to be used in steerers with a larger ID, say Cr-Mo instead of carbon. I know Profile Designs sold expander plugs in different OD's for use in various steerer materials and the ones for Cr-Mo steerers were larger.
I used one of their steel steerer expanders in my Surly Cross Check as an adjuster until I determined exactly where I wanted to cut the steerer and then replaced it with a starnut.