this seems to suggest that a stem bought with a built-in 12 deg angle would come with a shim that can make the resulting angle +8 or -16 deg, meaning the shim itself produces a 4 deg change either way
this would make sense given that my 3.38 deg spacer ended up working acceptably well
this is sort of weird because I think the shims being labeled +8/-16 is misleading since that depends on what stem they're paired with – unless such a shim is only compatible with a 12 deg stem
that's possible, but sounds somewhat stupid
maybe Specialized had a good reason for such a nuance
Rev 3
Added second indicator notch to make it easier to line up the wedge.