Stopper Tensioner Retrofit Kit for 13 mm chainstoppers. The 10-13 mm chain stopper is now available with integral anchor tensioner which is used to pull the stowed anchor tightly into the bow roller or anchor pocket preventing unwanted noise from the anchor pocket andunwanted noise from the anchor moving. A retro-fit kit is available to fit the tensioner assembly onto existing Maxwell 10-13 mm chainstopper bodies.