2 x Anti-siphon Devices. Fits under Freightliner Push & Turn Cap with 2.25 inch ID fill neck. Diesel fuel anti-siphon device. Fits below Freightliner push & turn caps. Unique one piece design is easy to install Holds the nozzle for fast fueling; no splash back No holes or gaps larger than 1/4 inch Heavy duty - made from coated steel