These Service Caster Series #20 Polyurethane casters offer various wheel sizes and mounting heights: 3” Wheel: 4-1/8” mounting height; 3-1/2” wheel: 4-5/8” mounting height; 4” wheel: 5-1/8” mounting height; 5” wheel: 6-1/8” mounting height; 6” wheel: 7-1/8” mounting height. Wheels are offered in five different colors – Gray, Blue, Black, Maroon, and Red. Weight Capacity: 3" and 3.5": 300 lbs Capacity/Caster; 4", 5", and 6": 350 lbs Capacity/Caster Top plate measures at 2-1/2" x 3-5/8" with a bolt hole pattern of 1-3/4" x 2-7/8" to 3" and can either be bolted or welded on. Brake options include a top lock brake, a total lock brake, or a posi lock brake. The top lock brake places a positive locking force against the wheel tread locking the wheel only. The total lock brake simultaneously locks the wheel and the swivel for a complete stationary position. The posi lock brake places a positive locking force against the wheel tread similar to the top lock brake, but the pedal is located above the wheel tread rather than on the side of the wheel. Find other wheel materials, sizes and all Service Caster products at our Amazon Storefront. Click on the “by Service Caster” link above the main title on any Service Caster page listing. Listing is for a set of four (4) Service Caster Series #20 swivel casters, four (4) swivel casters with total lock brakes, 5” diameter by 1-1/4” wide gray polyurethane wheels. Supports a total weight of 1,400lbs (350lbs/per caster). When searching for a reliable and durable solution to your caster needs, look no further than the Service Caster Series 20 top plate polyurethane casters. The Service Caster Series #20 is ideal for light and medium duty material handling, carts, equipment, and shop projects. The zinc plated finish provides durability under any condition, while the non-marking, non-marring polyurethane wheels perform especially well on hard surfaces such as concrete, tile, and wood- rolling on a finely crafted ball bearing design that keeps you moving forward. Service Caster is unsurpassed in quality, reliability, and excellent customer service. Count on us to move you forward.