These Service Caster Series #20 Semi Steel Cast Iron casters offer various wheel sizes and mounting heights: 3” Wheel: 4-1/8” mounting height; 4” Wheel: 5-1/8” mounting height; 5” Wheel: 6-1/8” mounting height. Weight Capacity: 3", 4", and 5": 300 lbs Capacity/Caster All casters feature a 1/2” diameter (13 TPI x 1-1/2”) threaded stem. Threaded stems can be difficult to measure. Service Caster recommends having existing threads checked on a thread gauge to determine correct thread size before ordering. 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) places a positive locking force against the wheel tread locking the wheel only. The total lock brake (TTL) 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 one (1) Service Caster Series #20 swivel caster with a 3" diameter by 1-1/2" wide semi steel cast iron wheel and a 1/2" threaded stem capable of supporting 300 lbs./caster.When searching for a reliable and durable solution to your caster needs, consider Service Caster’s Series 20 roller bearing semi-steel cast iron 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 semi-steel wheels are abrasion resistant and rugged, maintaining effortless rolling under heavier loads, and provides a cost-effective solution over steel wheels. The roller bearing is capable of carrying greater loads while also providing smoother rolling motion. It has a split outer race shell into which the roller assembly is inserted. Combination seal/thrust retainer washers protect the bearing from dirt, water, and chemicals. They also help absorb thrust friction (Note: roller bearing must be used with hardened spanner bushing or hardened shaft). Mounting options include top plate, bolt hole and standard and metric threaded stem sizes. Service Caster is unsurpassed in quality, reliability, and excellent customer service. Count on us to move you forward.