... well 2)metal seal or rubber seal 3)used to drill low compressive strength kingdream14 3/4" Newest IADC 537 TCI Tricone ... 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 7/8",12 1/4",17 1/2 ... ", etc. IADC Code:4-- Series, 5-- Series, 6-- Series,etc. kingdream14 3/4" Newest IADC 537 TCI Tricone bit