These 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. Brackets will fit onto any height and virtually any width I-beam trailer frame.Features Mounting hardware included Sold in pairs Adjusts out to 19 in. each side 1.5 in. square. 16 gauge pre-galvanized steel uprights 2.4 in. diameter white PVC posts. Installation Instructions