MRP AMg SL Chainguide - 28-32t ISCG-05 Aluminum Backplate. The MRP AMg SL chainguide eliminates dropped chains and bent chainrings. It combines a lightweight upper guide and a durable bashguard mated to an aluminum backplate. Unlike the cheap flexy and rattle-prone upper guides found on other products the AMg features our premium stiff silent upper guide and a tough fiber-infused bashguard.