Promax C-1 Chain Tensioner
C-1 chain tensioners are extruded then CNC-machined from 6061-T6 aluminum for optimal strength and low weight. Two mounting holes ensure perfect adjustability on most frames. When used properly, they will protect your frame dropouts and help hold your rear wheel in place.
Great value, works perfectly on my Transition Klunker with a longer chain. This was due to the short chromoly dropout. I had to add a larger sprocket and longer chain anyway, and now everything is perfect.