I bought 4 to use on my Roland rack with some some toms I'd converted from pearl mount, and they don't grip well enough. I tried on another rack which uses Gibraltar tom arms and they grip better, but still not perfectly. Plus, when off the rack the tightening mechanisms flop-around, and if they come undone you could lose parts.
I would recommend them only for floor toms, with decent grippy legs, and only if you don't want to spend a few extra euro on better ones.