Dixon Bayco Tightfill elbows with locking handle and female coupler. Strong arm design increases the strength of the locking arm components. Arm hinge points use a double yoke designed to increase strength. There are no side bolts or casting bosses to break. No need for the operator to engage or set the locking mechanism because the 6500 series automatically locks the arm onto the fill adapter when the arm is rotated into the locking position.