Hobbypower CNC Alloy 25mm Tube Boom Mount Motor Clamp for DIY Quadcopter Multirotor (Pack of 4 Pcs) For 25mm diameter tube Dimension: approx. 37 x 31 x 5 mm 3-Axis Aircraft: need 12 pcs Quadcopter : need 16 pcs Hexacopter : need 24 pcs