Our dual bolt clamping hubs work great to attach gears, sprockets, wheels or other items to hollow 1/2” or 5/8” aluminum tubes. The tube clamp has four (4) equally spaced 6-32 tapped holes. Precision machined from aluminum. These clamping hubs offer several advantages over set screw hubs. First, they do not damage the shaft which they are attached. Second, they offer more holding power in high torque applications. The side clamping machine screw is 6-32 and accepts a 7/64” hex key.