Electroplate diamons drill bit
As we made the diamond bit with these advantages, widely used in geology and mineral exploration, water development and roads, railways, bridges, housing, construction, core-pulling experience bored through solid rock 
Specifications with Inch 2-15/16", 3-5/8" 4-3/9", 5-1/9"  5-9/10"  6-7/10" 8-6/10"