Specially Designed Wrenches for Removing and Replacing the Main Filter Collar as well as the Vent Cap on Aftermarket Diesel Fuel Filter Systems. 8" wrench with a unique half-moon design provide easier access to the fuel filter. High strength steel prevents the wrench from flexing while loosening stubborn filter collars. Four teeth grab the vent cap securely to prevent damage. 8" wrench works Detroit Diesel DD13, DD15 and DD16 engines found in Paccar, Daimler Trucks North America, and Volvo.