"Spring loaded mounts retract to cushion boats and prevent damage" ShocStop Mounts: The heart of the Dock D'Fender is the patented mounting system. What makes this system truly revolutionary is that the ShocStop mount actively absorbs force and cushions boats. The ShocStop mount's spring loaded mechanism is precisely calibrated to start cushioning a boat before damage can occur. Unlike fenders which will only deflect force, the spring loaded ShocStop assembly actually retracts to absorb impact instead of passing it on to the docked boat. When used with inflatable fenders, this provides superior protecton during docking and long term mooring. "Dock D'Fenders are available in 27" or 30" long fenders and can be tailored for the size of boat that they are designed to protect. All Dock D'Fenders are constructed using marine-grade aluminum, corrosion resistant hardware, and soft vinyl fender to provide long lasting and reliable protection." "Spring-loaded mounts hold fenders securely in place at all times while providing superior cushioning during impact." Soft polyolefin scuff guards cover metal components and provide added protection against scratches and damage. Scuff guards are standard on all Dock D'Fender models.