CURT Protective Tailgate Sensor with 2 1 2" Hitch Cap, Fits Select Chevrolet Multi Flex, GMC Multi Pro Model 58268 Gloss White Truxedo Deuce Tonneau Cover Portable Magnetic Mount Shoe Truxedo Deuce Tonneau Cover Black 2014 2018 (2019 Legacy Limited) Chevy Silverado GMC Sierra 5' 9" Bed Model 771801 This kit gives you four total rails to mount two per side or use them as top rails This hitch cap sensor detects if there is a hitch accessory installed in the receiver tube and prevents the inner tailgate from folding down and hitting the ball mount or other accessory This Chevrolet GMC tailgate sensor installs easily with everything included in the kit