... 1.Sizes range from 3 7/8" to 26" , 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 ... sealed bearing or roller non-sealed bearing.4.Used for mining, hydrology, subterranean heat,piling, water well drilling and oil well ...