This is a replacement for plastic wheels that we installed just over a year ago and which began to fail a few months after installation. We bought these wheels as a spare and after a week we can safely say they are GREAT! We have a dual 6-foot log driveway for privacy, spans of 10 feet each, and new 6-inch hard rubber wheels glide effortlessly over our concrete without hitting or rattling. Everyone. We are very impressed and they are worth it, we bought two. They are very well made and designed for tough use.