C.E. Smith 75" Guide f/I-Beam Mounting [27635]75" Post Guide on These extra tall Post Guide Ons allow you to see the location of your trailer when it's under water. Designed for I beam trailers and I beam boat lifts, these guide ons feature an innovative two piece mounting clamp that works above or below the I beam. Fits on I beams up to 4" wide with provided hardware. Features: Mounting hardware included Sold in pairs Adjusts out to 19" on each side Fits frames up to 3"W x 5 1 4" H 1 1 2"