... 1-a large stock 2-good quality&certified by API 3-short delivery time Product (1):we specializes in manufacturing: ... , tungsten carbide insert rock bit, tri-cone drill bit , 3 cone bits, rotary bit, TCI tricone bit, PDC drill bit ... bit, 4-wings drag bit optional. Shapes can do chevron & step as requested. Sizes: 3 3/4", 3.7/8", 4", 41/4", ... 55/8 ", 47/8", 6", 7.3/8", 4.3/4",5.1/8", 5.5/8", 5.7 ...