This page covers our 4" x 2" High Performance Polyurethane Wheels Mechanically Locked to an Industrial Polyolefin Core Wheel. The Maroon Colors are highly UV Resistant if these are going to be used in clean room operations or exposed to UV sanitizing lights as well as great for outdoors when exposed to the sun for long periods of time. The standard colors are also UV Resistant to a certain degree but not as resistant compared to the maroon color polyurethane. These Wheels are Liquid cast flow through 100% tread. 90-95 Shore (A) Durometer mechanically bonded to the polyolefin core. Our Polyurethane Wheels are light weight but offer a high capacity. Polyurethane on Polyolefin Wheels are resistant to oil, grease, water, blood, up to 10% acidity, and most solvents. Our wheels are completely non-marking, non-marring, smooth rolling and very quiet. Multi-year tread durability. Various color are available. These wheels should only be operated under temperature ranges from -45 degrees F up to 180 Degrees F. The Casters that we provide with these wheels contain a double ball bearing raceway combined with a rust resistant zinc plated finish. 5/8" Diameter permanent riveted kingpin for increased durability and strength and 1/4" thick cold forged steel top plate and yoke legs. All of our 2" Wide Casters and Wheels come with heavy duty 1/2" Diameter zerk axles and lock nuts. The mounting plate size offered in this listing is an industry standard 4" x 4-1/2" overall mounting plate size with bolt hole dimensions of 2-5/8" x 3-5/8" slotted to 3" x 3". The attached bolt hole size is 3/8" and you can choose to add the mounting hardware for an additional cost from our drop down box on the right hand side of each product page. We offer many upgrades including Top Locking Brakes, Total Locking Brakes, as well as 4 Position Swivel Locks if you are looking to convert your swivel caster into a fixed caster when needed. The wheels come with a standard 3/4" Roller Bearing standard but you can also choose to upgrade to a sealed precision bearing in your wheels if you would like a easier rolling and quieter rolling wheel. Roller Bearings are typically optimal for most standard duty applications but if the application is heavy and your cart or equipment will be moved manually the precision bearing upgrade is always a great choice to reduce push/pull force and generally offers a smoother ride while eliminating the need to grease your bearings as you would need to do periodically with a standard roller bearing.