Package Included: 4pcs Standard Countersinks and 4pcs 4 Flute Countersinks. Countersinks make tapered plugs to fill countersunk holes. Diameter sizes include 6mm/10mm/13mm/16mm (1/4 , 3/8 , 1/2 , 8/5) Shank Diameter: 9.3mm8pcs Cutter Set: Makes perfect plugs for drilled holes. Easy and safe to use and store. Material: Carbon steel, titanium coated, durable and high precision. Reduce drilling resistance, reduce heat, bit more durable.luckymeet