... structure features of more than 17 1/2 disc bit: drill for a style, level 3 rolling bearing ... main structure features of more than 12 1/4 disc bit: :for no drill style, level 3 rolling bearing ... structure features of less than 12 1/4 disc bit: drill for no style, level 2 rolling bearing, ... sliding, steel ball lock, suitable for high speed.4.Bit bearing no seal, drilling fluid directly into bearing cavity ...