Secure Drop Coupler. High Tensile Aluminium. Parallel StyleDrop Length: 500mm Fits bar size::- 48-51mm SWL: 200kg. A 500mm parallel pipe coupler providing a firm coupling between two parallel bars. Constructed from high tensile aluminium extrusion. Factory welded half couplers capable of accepting bars with external diameters from 48mm to 51mm.. doughty fixing-doughty trussing