1. We choose YK05 tungsten carbide buttons, their features: high footage speed, high wear resistance, Suitable for 98% rocks(especially for hard rock) 2. Material:35CrNIMoV 3. Flushing Holes:2 or 3. 4. Thread Type: CIR,DHD etc. 5. Carbide Length:0.5mm longer than other manufacturer so the carbides won't come off.1. Drop Center Bit For high penetration rates in soft to medium hard and corrosive rock formations. Low to medium air pressures. Maximum hole deviation control. 2. Concave Face The all-round application bit face specifically for medium hard and homo generous rock formations. Good hole deviation control and good flushing capacity. 3. Convex Face For high penetration rates in soft to medium-hard with low to medium air pressures. It is the most resistance to steel wash, and may reduce the load and wear on the gauge buttons, but poor hole deviation control. 4. Double Gauge Face This kind of face shape is suitable for fast penetration rates in medium to hard rock formations. Designed for high air pressures and good resistance to steel wash step gauge bit. 5. Flat Face Bit This kind of face shape is suitable for hard to very hard and abrasive rock formations in applications with high air pressures. Good penetration rates an resistance to steel wash.