From the product description, check product page for current description, price and availability:

• The Slim Keg Dolly is great for relocating Sixtel kegs and Slim 1/4 Barrel kegs from a storage cooler to an outlet beer kegerator or for moving kegs when mopping walk-in coolers.
• These black Keg Dollies are much better than the red keg dollies you’ll see on the internet. Ours are made of reinforced durable plastic that will hold 2 slim kegs without a problem. They have been approved to roll up to 300 pounds.
• The 5 casters have non-marking polyurethane wheels which are superior to the red dolly’s rubber wheels that eventually wear down. One of the casters has a brake to stop rolling on uneven floors. In addition, the wheels have an axle bearing rather than a singular axle pin that makes them able to endure more use without seizing.
• We like to call this keg dolly our “Holy Roller” since it is designed with ridges and open slats to allow drainage for condensation that accumulates on the kegs. You won’t find the wheel brake or the open slats on any other keg dolly and the black color keeps the dollies looking clean.
• These can also be used as plant dollies but never use a plant dolly for kegs! That would be a waste of your hard-earned money.