This roller assembly supports your boat's keel for easy loading and safe transport on your trailer. Typically installed flat on the tongue of a boat trailer, this spool roller bracket assembly stabilizes the keel of the boat during trailering. The roller assembly features a 4”, rubber spool roller and a galvanized steel bracket to attach to a 2 - 2 1/2" trailer tongue. Features:Spool roller supports the boat's keel as it sits on the trailerBracket fits 2 - 2 1/2" trailer tonguePrevents the bow from making contact with the winchEases loading and unloading of boatHelps to absorb road shock while boat is being traileredBracket allows bolt roller assembly onto the tongue or frame of your boat trailerSturdy, 1/8" galvanized steel bracket resists corrosionBlack rubber roller delivers long-lasting performanceRequires 7/16" fasteners (not included)Made in the U.S.A.Specifications:Roller Dimensions: 4"WShaft Dimensions: 5/8"dia.Mounting Hole Dimensions: 7/16"dia.Mounting Hole Spacing: 3" apart on center