The Peterbilt Ultracab XL Economy 4 Inch Conversion Kit is a practical solution for those looking to extend their cab. This kit includes a pre-assembled fiberglass panel with a pre-installed sound deadening core, making installation a breeze. The CNC cut and drilled panel ensures a precision fit inside the rivet line, and the kit comes with all necessary hardware and sealer. The Class A gel coat finish and gray vinyl interior give the cab a sleek look. This kit fits most Peterbilt Ultracab XL Economy models and includes an 8.5 inch by 22.25 inch window.