Drop Elbows (also known as Tight Fills) connect to the underground tank fill collars to the tanker drop hose. They allow convenient hose connection and prevent hose damage due to kinks. There are 2 types of systems for filling underground gas station fuel tanks: dual point (vapour recovery and fuel drop are done at 2 separate areas with separate elbows) or co-axial (vapour recovery and fuel drop are done using the same elbow at a single point). These have a strong arm that automatically locks when it is moved into the engaging position.