I just bought six Saturday. They listed for $11.49, but sold for $7.00.
When asked IF I could trade in (swap) my old ones (apperantly, this DOES happen often), they said "HELL NO!"
They showed me with a straight edge how mine were worn, with a concave shape where the Cam Lobe wears in the center, and NO WEAR at the edges, due to 23,000 miles of use. Then asked, "Can we sell you someone elses used, concave shims, even after determining the thickness?"
I sure as heck WOULD NOT accept used ones, with thousands of miles wear. Would you, cause I do have six used ones, and the thickness is marked in Sharpie on both sides.