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 All casters feature a 7/8” x 2” square stem with (3) 17/64” diameter mounting holes. Don't see the size you need? No problem! Call us or message us by clicking the blue Service Caster Corporation hyperlink underneath the buy or add to cart button and then clicking the ask a question button. 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 four (4) Service Caster Series #20 swivel casters with a 5” diameter by 1-1/4” wide black polyurethane wheels and a 7/8" square stems. Supports a total weight of 1,400lbs (350lbs/per caster). When searching for a reliable and durable solution to your caster needs, consider Service Caster’s Series 20 square stem 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. The square stems are designed to be bolted or riveted onto the inside of angled iron legs or against any flat surface. All rolling on a finely crafted ball bearing design that keeps you moving forward.