Heavy Duty Tube Bridgestone 80/100-21 - TR-4 Valve Stem NOTE - SAFETY WARNING: For information on tire care, safety, maintenance, mounting, manufacturers warranty and other information consult tire manufacturers publication(s) and/or website(s) for complete tire information. The tires used for your application must have a load index and speed rating equal to or greater than the tires fitted as original equipment. Motocross - Heavy Duty Tube Size - 80/100-21 Valve Stem Type TR-4 Straight metal stem (8mm dia.) IRC and Dunlop