The important part is that the tightening of the U-Bolts will prevent your guide poles from moving. It is also not uncommon to have to get U-Bolts that are wider than or longer than your frame. If you are wanting to mount this guide post to a Square tubing or C-Channel shaped frame, you will be needing a 1 1/2 inch Galvanized Boat Trailer Hat Bracket with the correct height and width of 3/8" diameter Boat Trailer U-Bolts that will fix around your frame. Easily load your pontoon boat onto the trailer for your next boating trip with the Extreme Max Industrial Steel Boat Trailer Guide On. The combination of Aluminum against aluminum with stainless steel will be the longest lasting guide pole system possible. If you are mounting this Aluminum Guide Post to an aluminum I Beam trailer frame, the simplest way is by using (2) Stainless Steel Square Ubolt 3/8 inch x1 9/16 inch x 2 1/2 inch to drill directly into the I-Beam. This Guide Pole is bent at 90 Degrees for perfect alignment with the side rail of your boat. This is for (1) single replacement guide pole. The guide poles typically attach via u-bolts to the main I-beam frame or into a cross member. Extreme Max 3005,2181 Roller Trailer Guide-On, Pair: Automotive,Online watch shopping,satisfaction guaranteed,Quick delivery,Lightning fast delivery. The bunks of the system feature pressure-treated wood. The manufacturer is committed to ensuring your boat safety while bumped against. Providing two 18 carpeted bunks, this single post bunk guides system keeps your boat lined up properly. We are proud to offer the best quality pontoon trailers that are ranked at the top of the boating industry. This extreme Max guides system matches trailers with frames up to 3 wide and 4.25 high. We also have delivery options if you need a pontoon trailer shipped to you. The pvc sleeves are available separately. We welcome pickups at our corporate office in Mishawaka or in Lebanon, Missouri. The trailer guide-ons by Extreme Max is one product which will make loading and launching your boat to and from the trailer to the water extremely easy. This guide pole is designed to have 2" pvc slide over top of it. It has an aluminum welded tab to serve as a stop for your pvc. It measures 46" tall and has a 24.5" long leg for easy width adjustment to fit the sides of your boat as is goes onto your trailer. This replacement boat trailer guide on pole is manufactured out of 1 1/2" square aluminum tubing with 1/8" wall thickness.