Summary

Brake pad spacers for bleeding single-piston Shimano calipers.

These are in two parts, because it makes it easier to get them in and out of the calipers without removing the calipers from the frame, plus you can stack them into any thickness you like (10mm is the correct thickness for my calipers, but with these four shims you've got options from 7mm to 11mm)

Disclaimer: Don't work on your own brakes if you don't know what you're doing, you might die and also you might scratch your bike.