These are awesome.. I love the knurled magnetic hitchpins, the quick attach handles and weight horns and the 360 motion, which can be locked so they do not flail around.
They solve so many of the traditional problems with jammer arms, by providing the "circle" with holes to adjust starting points.
Besides all the machines these can emulate, and feel awesome too, the eyelit in the end offers makes each arm a stable plateloaded cable-trolley. Add a pulley and a cable to your rack, load the jam...