... cutters optimal designed highly increase efficiency of drilling.3. Oppose-circumnutation design. The load on bit is balanced, and journal libration is decreased ... drilling. Type and Features PDC bit can be customized for oil well, water well, mining, explorer well drilling. Suitable Formation Various ... Sizes: 5/16" (8mm), 1/2" (13mm), 5/8" (16mm), 3/4" (19mm), etc. Blades: 2~9 Wings.