SizeInner roller is 4inch wide, the inner diameter of mounting hole is about 1.3cm/0.5inch. Fits 4 inch wide center roller bracket. Overall width about 18cm/7.09inch MaterialThe boat trailer bow roller is made of nylon material, which is sturdy and wear resistant. It's lightweight yet has a strong load bearing capacity, making it reliable for long term use Smooth & Noiseless RollingThe Boat Trailer Roller ensures the boat run smoothly on the trailer, and can help you cushion and protect your boat, yacht trailer accessories Easy to InstallThe boat trailer roller is easy to install and use, you can easily tow your boat, improving work efficiency while saving energy and time Wide ApplicationThis boat trailer bow roller marine boat tug roller is widely used for transporting large cargo in factories, docks, ports, warehouses and other production areas. suitable for boats, trailers, ships, yachts Specification: Material: Nylon Size Chart: Inner Roller Width: 4inch Total: 18cm/7.09inch Inner Mounting Hole Diameter: about 1.3cm/0.5inch Package Includes: 1 Piece Boat Trailer Roller Note: Please allow slightly errors due to manual measurement and different monitors.