4/0 Gauge Non-Insulated Ferrule .6772 Inch Inside Diameter 1.26" (32mm) pin length 4/0 gauge non-insulated ferrules, 1.26" (32mm) pin length. Use these ferrules to prevent wire ends from fraying or breaking. The tin-plated copper tubes make for an easy mating point with terminal blocks, or under set screws and pressure plates. Ferrules also hold up to vibration, can be reconnected multiple times without damage and are a stronger mechanical connections than ring or fork terminals.