Cargo Management - DUHA Underseat Chevy Silverado/Gmc Sierra Crewcab 07-11 (Lt Gray) is custom designed to fit a particular model of truck. The Chevy/GMC Extended cab C/K model DU-HA is designed to fit underneath your pre-existing back seat. It is constructed from heavy duty polyethylene and comes with a lifetime warranty. The factory jack box needs to be improved from underneath your seat to install the DU-HA. This model also acts as a legal gun case in most states and will hold up to 3 guns.