Manufacturer Description The RAM-235-1U LARGE Dual Zinc Coated U-Bolt Pipe Mounting Base is designed to fit a 1.25 inch to 1.5 inch diameter round pipe. The base is constructed of Marine Grade Aluminum with a Black Powder Coating and has a 1.5 inch diameter Rubber Ball. For extra holding power, the base connects to a pipe with two zinc coated 1.5 inch u-bolts.