Noga Reversible Countersinks.

Patented rotating blade system enables the blade to be set in position to deburr either the front face or back face of a hole
A rugged knurled steel body is fitted with a replaceable Countersink Blade and incorporates an end button for blade positioning

Countersink Blade angle 90 ̊
Three individual models are available which cover the countersink diameter range 3 – 22mm