I have used one of these, they are cheap, but they work quite well, i did find it slipped on 4" pipe so it had to be fairly tight, can't really use it on anything below 4", but for the price and 12" pipe it worked quite well, only thing about it was making sure the chain was tight and inline, if it has any lateral bow, it will slacken up and it will cut crooked, but if ya tighten the chain and swing it back and forth a few times it pulls the slack and u can re tighten and re align it and it cuts pretty darn good.