Hobbypower CNC Alloy 16mm Tube Boom Mount Motor Clamp for DIY Quadcopter Multirotor (Pack of 4 Pcs) For 16mm diameter tube Dimension: approx. 28 x 23 x 5 mm 3-Axis Aircraft:need 12 pcs Quadcopter :need 16 pcs Hexacopter :need 24 pcs