Chain Stopper Diagram Chain Stopper for chain 9mm – 13mm / 3/8″ – 1/2″ Works with your anchor rollers to take the tension off the windlass by locking the chain. Handles 9mm – 13 mm (3/8” – 1/2″) chain. Included a convenient foot tab for safe and easy operation. Mounted with 4 screw holes to increase breaking strength. Made in 316L mirror polished stainless steel.