This ring is only compatible with our steel bird cage. You can find our full range of back rings here that will fit different cages. Using a kit that fits you properly is essential for comfortable, long-term wear. It's also important to consider that different factors can effect the best size for you. For example, warmer or colder weather can change fit. Sometimes a slightly tighter or looser ring and cage size can ensure that you remain comfortably locked. Need help finding the right size for you? Please carefully read our read our measurement guide before you order. If you want a second opinion or additional help please don't hesitate to get in touch with us and we'll do all we can to help. We're offering this back ring in 40mm, 45mm and 50mm sizes. They can be ordered at the same time you buy a kit or later if you find that you need a different size.