The Leofoto MG-40 Rifle Ball Head is purpose-built for heavy equipment support from the ground up. It comes with a hybrid, dual clamp for both arca-type and picatinny rails with a twist knob clamp lock. The MG-40 features an oversized, knurled, twist knob which has separate tension control on the side of the knob for the perfect amount of friction. Height:105mm / 4.13 inchesBall diameter: 40mm / 1.57 inchesMounting hole: UNC3/8", M4Weight:450g / 1.16 lbsMax load: 20kg / 44.09 lbs Leofoto MG-40 Rifle 40mm Ball Head MG-40-FOR-SA-TRIPOD