depends what application you're using one on. i have one and for about a year i climbed with it in place of a prussik using 10.5mm mountaineering rope. it shouldn't be used this way as its not designed to be shockloaded.....however if you're climbing with enough slack in your system to subject anything to that much shock loading then you're climbing wrong anyway! but anyway in answer to your question, yes it works, never had it slip on me and id so give it a try. only reason i really stopped using it was because i switched to fly rope and it didnt run too smoothly in the shunt