The Peterbilt Unibilt XL Economy 4 Inch Conversion Kit is a practical and efficient solution for enhancing your Peterbilt Unibilt XL Economy model. This kit includes a 4-inch cab extender, a pre-assembled fiberglass panel, and an 8.5-inch by 22.25-inch window for added convenience. With a pre-installed sound deadening core and CNC cut and drilled panel, this kit ensures a precise fit inside the rivet line. The gray upholstery and class A gel coat finish add a touch of elegance. Sold as a kit with all necessary hardware and sealer, this conversion kit is compatible with most Peterbilt Unibilt XL Economy models.