Mercury – GPS Extension Cable | 3.2-Foot CAN P Line | 84-879171T21Mercury GPS Extension Cable 3. 2 Foot CAN P Line 84 879171T21 Overview Sometimes the factory cable on a GPS antenna just does not reach the spot where the signal is strongest. The Mercury 84 879171T21 Extension Cable gives you a little more room to work withjust over three feetwhich is often exactly what you need to get the antenna into clean sky. Its made for boats running the 8M0024918 GPS Kit and carrying a CAN P signal, especially setups without