Katu Carpet Wheels for Office Chair Casters Model B503-38. Standard Stem 11 MM (7/16) Heavy Duty up to 110 Lb Max Weight (Set of 5) Twin caster wheels standard replacement for low carpeted floor or hard surfaces. Not safe for hardwood floors. Standard stem size: 11mm (7/16") diameter, 22mm (7/8") length with 2 inch diameter wheel. Maximum Weight Rating: This office chair wheels supports 110 lbs. per wheel (Set of 5 supports 550 lbs.) Shaft lubricated with Lithium based grease for smooth and easy movements. Tested for quality: Katu Casters are tested before production so we are confidence to offer 5 years warranty.