X8 (formerly X8.99): stretchproof, chamfered plate, fullnickel plated chain for 58 speed and great for internal geared hubs\n Z8.1 silver/gray (formally Z72): chamfered inner plates with Bullseye rivets for 58 speed\n Z8.1 gray (formally Z51): standard bushingless, chamfered plate chain for 58 speed\n Z30: economy bushingless chain for 58 speed\n Z7: high pin power with reinforced durability and quieter riding experience, smoother shifting