These bunk-style guides are designed to support your pontoon boat and keep it centered while you're loading it onto your trailer. While installing you can set the height between 24'' and 36'' above the frame for a better fit to your boat. Support posts clamp onto the top of channel box-beam or I-beam trailer frames up to 3''W x 4.25''H. The mounting bracket lets you adjust the distance between the posts. Constructed of sturdy corrosion-resistant galvanized steel with marine-grade carpet to protect your boat. Includes two carpeted 24'' bunks and all necessary zinc-plated hardware. Made in the USA.⢠Bunkboard Dimensions: 24''L x 4''W x 2''D⢠Post Dimensions: 23''L x 1.5''W⢠Mounting Area: 9.5''L⢠Mounts to frames up to 3''W x 4.25''H (For mounting to I-beam frames larger than 3''W x 4.25''H use the I-Beam Clamp Kit item #316576 sold separately)Features: Guide your boat effortlessly onto your trailerFit I-Beam Box and Channel FramesGalvanized steel constructionIncludes all zinc-plated hardware | Pontoon Boat Trailer Bunk Guides, pair Made in USA