Series G236 HSS Countersink Set. Straight Shank 3flute, 90° Countersink. Set 1 (G136) in bright finish improves chip flow in soft ferrous & non-ferrous materials. Tri-Flat Shank Sizes 6.3mm,8.3mm,10.4mm,12.4mm,16.5mm,20.5mm. Manufactured to DIN 335C.