High quality replacement caster set for Knacck casters Model 516. Listing is for a set of four (4) Service Caster Series #30 casters with a 6" diameter, 2" wide polyurethane tread set on polyolefin core wheels. Set includes two (2) rigid casters and two (2) swivel casters fitted with top locking brakes . Supports 3,600 total pounds (lbs) at 900 pounds (lbs) per caster. Non Marking/Non Marring. When searching for a reliable and durable solution to your Knaack replacement caster set needs, consider Service Caster Series 30 polyurethane wheel casters. The Service Caster Series #30 features heavy duty non-marking polyurethane tread on a polyolefin core wheel, providing a smooth roll over uneven surfaces without marking or marring floors. These versatile casters are ideal for a wide range of applications, such as dollies, platform trucks, warehouse carts and freight terminals. Or ensure a smooth and secure ride for food service carts, hotel housekeeping carts, and industrial and commercial equipment. Even drywall carts, welding carts, and wall panel carts will be ready to roll on the Series 30, keeping you moving forward. Service Caster is unsurpassed in quality, reliability, and excellent customer service. Count on us to move you forward.