Ultra Fast To Fit. TUV Approved. Captive Securing Bolt. No Tube DamageSWL::- :- 20kg Tube diameter:- 48-51mm. This Doughty Clamp can be secured to tubes with just two turns of the knob. Luminaries are secured via a captive M10 Bolt. Damage to tubes and truss is eliminated by using an extruded trigger. TUV Approved