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 (TLB) or a total lock brake (TTL). The top lock brake (TLB), which is featured on 3", 3-1/2", 4", and 5" wheel sizes, places a positive locking force against the wheel tread locking the wheel only. The total lock brake (TTL), which is featured on all wheel sizes, also places a positive locking force against the wheel tread, but the total lock brake (TTL) simultaneously locks the wheel and the swivel for a complete stationary position. 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 stainless steel casters, two (2) swivel total lock brake swivel casters and two (2) swivel casters, with 3” diameter by 1-1/4” wide Black polyurethane wheels. Supports a total weight of 1,000lbs (250lbs/per caster).When searching for a reliable and durable solution to your caster needs, consider Service Caster’s Series 20 stainless steel threaded stem polyurethane casters. The Service Caster Series #20 is ideal for light and medium duty material handling, carts, equipment, and shop projects. The threaded stem is available in standard or metric sizes and ensures a solid and secure attachment. The polished stainless steel 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. All rolling via a finely crafted ball bearing design that will keep you moving forward. Service Caster is unsurpassed in quality, reliability, and excellent customer service. Count on us to move you forward.