Blue Spot 77077 Square Link Chain 3ft x 8mm Features and Benefits: Manufactured from hardened steel with a nylon sheath for protection and increased durability. The square links are 8mm in diameter and are suitable for domestic and industrial use, the square profile also makes it harder to use bolt cutters on the chain itself. 8mm hardened steel links. Nylon sheath for increased protection. Suitable for domestic and industrial use.