... will improve the reliability and durability of bearing seal.Main Type Available Size: 6",6 1/2",7 1/2",8 1/2",9 1/2",9 5/8",9 ... /8",12 1/4",17 1/2", etc. IADC Code:4-- Series, 5-- Series, 6-- Series,etc. 2. Elastomer sealed bearing TCI BitCutting Structure The durability ... can enhance the seal performance. Main Type Available Size: 5 7/8",6",6 1/2",7 1/2",7 7/8",8 1/2",9 1/2",9 5/8 ...