The clamp size is 2 inch, we supply 2 rubber inserts for 1″ to 1-1/4″ inch size tubing. Stainless Steel;Adjustable Fishing Rod Holder for Rails 1″ to 1-1/4″. The 5 rod holders will clamp to your T-Top, hardtop, tower, radar arch, rail or any structure made from 2 inch tube pipe (without insert), 1.5inch-1.75inch pipe (with insert). You will have a place for you fishing rods in a safe place off your floor;Stainless Steel Clamp On Adjustable Fishing Rod Holder for Rails 1″ to 1 1/4″. It Can Adjust to Any Angle. Item Package Dimensions L x W x H. 44.5 x 11.25 x 4.45 inches.