Selens 40 inch 100cm Carbon Fiber DSLR Camera Slider Rail Track Dolly Video Stabilization Extensible -- There are 1/4 and 3/8 screw holes on the buttom and side Lock Button Design -- double lock button design to improve stability 8 Strong Carbon Fiber Tubes -- 8 layer carbon fiber tubes, which could support huge weight, max load 22lbs 6 Bearings Design -- One inner pulley and two outer pulleys are fixed respectively on each carbon fiber tube, which can effectively prevent the carbon fiber tube from being outward expansion after long time use Multi-level Adjustment -- This dolly track's four feet's adopt the multi-level adjustable system, not only apply to various occasions, but also can quickly adjust the angle on the uneven ground to ensure the Dolly Track could be work on the horizontality