Quick Release - you can change your watch strap in a flash. This is a quick-release FKM Rubber watchband having a cylindrical push button on one side for quick and easy installation and removal process without applying any tools. Not only that, this special made quick release spring bar having a double flange on one side which adds benefit in case there was a need to use a spring bar tool as well. FKM - Fluoroelastomer, which is a class of man-made rubber of great density, made to stand harsh conditions, such as high temperature and chemicals, etc. FKM rubber is often used in aerospace and nautical industries, which speaks a lot about its quality. They are waterproof, great for outdoor use and that's why FKM straps are highly popular among divers and adventurers. Certainly, this is one of the best Rubber replacement straps that work well with your RX or IWC.