This is the all new Primo Superior Caster Wheel Assembly composite soft urethane caster. Sold in Pairs with 5/16" bearings included. Fits All Sunrise Medical Wheelchairs (Quickie) Fits Invacare Wheelchairs, Fits Tilite And Ki Mobility Wheelchairs, Others. Qty of 2 Designed for those who want the ultimate smooth ride, these Ultra Light Aluminum Wheels feature an attractive aluminum hub and highly resilient, soft but solid urethane tire that will never go flat and help to minimize energy loss and absorb vibration. To improve pivot ability, the contact surface is spherical and features an arched tread design. This WIDE model allows the wheels to maintain higher flotation by better distributing downward pressure, which helps keep the user from sinking into carpet, soft ground, etc. CW501- 3" Tall Diameter X 1" Wide Aluminum 3 Spoke Rim W/Black Urethane Tire CW502- 3" Tall Diameter X 1 1/2" Wide Aluminum 3 Spoke Rim W/Black Urethane Tire CW503 - 4" Tall Diameter X 1" Wide Aluminum 3 Spoke Rim W/Black Urethane Tire CW504 - 4" Tall Diameter X 1 1/2 Wide Aluminum 3 Spoke Rim W/Black Urethane Tire CW505 - 5" Tall Diameter X 1" Wide Aluminum 3 Spoke Rim W/Black Urethane Tire CW506 - 5" Tall Diameter X 1 1/2" Wide Aluminum 3 Spoke Rim W/Black Urethane Tire CW507 - 6" Tall Diameter X 1" Wide Aluminum 3 Spoke Rim W/Black Urethane Tire CW508 - 6" Tall Diameter X 1 1/2" Wide Aluminum 3 Spoke Rim W Black Urethane Tire