... " , normal sizes consist of 5 7/8", 6", 6 1/2", 7 1/2", 8 1/2", 9 1/2", 9 5/8", 9 7/8", 12 1/4",13 5 ... /8", 14 3/4", 15 1/2", 16", 17 1/2 ... for mining, hydrology, subterranean heat,piling, water well drilling and oil well drilling, construction foundation etc. .We are experienced on manufacturing ...