Dresco bike chain tensioners to easily tension the bicycle chain. These traditional tensioners are attached with the ring to the rear axle of the rear wheel. Then place the bracket against the rear fork and tighten the nut so that the chain is correctly tensioned. Make sure that the chain is not tensioned too tight and that you can push the bottom of the chain up about one centimetre between the front and rear sprocket. The chain tensioners are delivered per 2 pieces.