Patch cords are used to provide air from the motorhome to the BrakeMaster installed in the towed vehicle. If you're using a drop hitch, an accessory that extends the length of the towing system, or you have damaged your existing cord, replace it with one of these to ensure proper pneumatics for your BrakeMaster (sold separately). Includes a male quick connect fitting on one end, and a female quick connect fitting on the other. The 921004-88 provides an extra foot of reach for 88-inches total.