Tip Shim
When the tip no longer has a gap.
As a shear ages the tang on the upper jaw wears down and the recommended gap between the blades is not there. This shim can help prolong the need to weld up and resurface the upper jaw tang.
For this application they are made from special tempered steel and not the typical soft shim material.
.015 Tempered Steel Tip Shim $39