Finding a good 1" threadless stem is near impossible these days.

This shim allows the use of any 1-1/8" threadless stem on a 1" threadless fork.

FYI: When using a 1 1/8" stem and shim on a 1" steerer, you need to use a 1 1/8" top cap. If you’re putting any headset stack spacers beneath your stem, you’ll need to use 1” spacers.