This American made product is a huge improvement over other metal roof accessory attachment devices currently on the market. The clamp is one piece and does not require seem feeding up the panel. This patented design fits over the seam for a fast effortless installation. The RCT model will fit most every seam but is especially designed to fit T-Seams and Bulb seams up to 1.5" wide. Interior dimensions are 1 /4" wide X 1 3/8" high with a 1 1/2" wide seam channel. The aluminum Roof Clamp utilizes a Stainless Steel oval tipped screw that does not pierce or penetrate the panel; therefore it will not void the manufacturer warranty. This is the clamp to buy when you want to stock one size clamp to handle most applications!