The Stoltz 4in Keel Roller is designed for optimal support and protection of your boat's keel during transport. With a durable 5/8-inch diameter shaft, this roller ensures a secure fit on your trailer, minimizing wear and tear on your vessel. Crafted from high-quality materials, it offers excellent resistance to UV rays and harsh marine environments. The 4-inch diameter provides ample surface area for stability, making loading and unloading a breeze. Upgrade your boating experience with the Stoltz RP-4 roller, ensuring your boat stays safe and secure on the road!