Welcome to Defender Canada! 
Whitecap Chain Stopper - AR-6495 Item # 888152
Description
Used to lock the chain in place between the anchor and locker on deck.
Specifications:
- 316 Stainless Steel Chain Stopper
- Length: 3 1/8"
- Width: 2 1/2"
- Fastener: 1/2" (2) not included
- Pin Diameter: 1/2"