there a very good tensioner i bought one last year for that red norco 4x4 Full Suspension bike i built last fall.i built it up single speed with that tensioner ordered from norco at ABC cycles.it worked out great my friend bought the bike off me 3 days later after building it up.and converting it to single speed.the tensioner is a little tricky to set at first and takes a few good runs and drops to set it up fully.there are many positions for any gear ratio plus extra chain length to allow the rear travel of frame,so not to break the chain.plus maintain tension.but allow for rear travel and over tension of chain so it takes a few rides and big drops to fine tune it but once you get it in the exact spot you need it.once done it will stay and work well and it still works well on the norco bike i did i still have not had to move it since i set and tuned it very good product for single speed lovers like my self and my buy another this summer for my DH bike