Reese custom spacer kit is needed for wider trailer wingsets to ensure a snug fit with the Sidewinder pin box. Engineered for a perfect fit and tested to meet or exceed industry standards and backed by a limited lifetime warranty for years of trouble free use. Designed for Fabex 500 and 700 series, Lippert 1116, 0115 and 1716, RBW 7019 and 70208 Wing Sets.