Hayes (Hays) Radial mount brake vehicle compatible - sold as a 4 piece set
Ok, so yeah, your asking what do these do? well Since your caliper has a
tendency to have a bevel right inside the hole, these Washers go
between the bolt and the Caliper, Centering the Bolt Correctly:

So what does this mean to you?
The caliper is Locked in
parallel to the Bolt, allowing it to Fully Float and reduce brake drag.
And when combined with Titanium caliper bolts, the overall package is
SO much better.
NOTE: does not include the Caliper bolts - those are sold separately below