The trap door collector box is used in fuel cells or large fill plate tanks to protect against fuel slosh. The in-tank fuel pump or pickup tube is inserted into the container and the 3 check valves serve as trap doors keeping fuel contained in the box no matter what direction the vehicle is shifting. The 20-0151 Check Valves feature a large 1" ball for maximum flow. The 2 piece check valve housings are machined from billet 6061 aluminum and anodized for corrosion resistance. Unlike round drilled hole variations, this design features full travel slots to prevent the ball from getting stuck in the hole and to promote quick filling. For more information, go HERE.