This wheel is made from high grade steel parts and the bearing spins quite freely. It's good for chinchillas, degus, rats and other small ground animals. The bearing does offer some resistance (this is necessary for safety) so the smallest animals may have trouble getting it going. A rule of thumb for chinchillas is no wheels until 6 months of age or older. Steel was chosen for the ChillaWheel's construction as cheaper materials were found to bend and break and plastic is toxic to chinchillas. Steel was also chosen as it's very easy to clean and doesn't hold bathroom smells like wood does. The ChillaWheel is 16 inches in diameter and has a 4 inch textured running surface that's easily gripped by your pet's paws. It also has a sloped running surface to allow your animal's bathroom droppings to fall off the wheel during use. The wheel's flat surface is meant to keep your chinchilla's paws from getting caught between wheel wires and the size of the ChillaWheel is perfect for protecting your chinchilla's back from spine curving. This wheel does make some noise during use but it's no louder than a dryer or a microwave. However, if your pet is in your bedroom, we recommend the Upgraded Quiet model. The Original ChillaWheel is very safe and our own personal chinchillas have been running quite happily on it for years now. Each wheel comes with a free sample of our organic ChillaSticks and organic meadow hay. Our ChillaSticks consist of Organic apple wood chew sticks from a local Sacramento certified organic farm as well as a sample of meadow hay.