NOTE: In an unforeseen trailer emergency or accident, when the coupler or hitch fails on a towed trailer, the last thing that should detach from the tow vehicle is this 44"cable, which fastened separately from the chains, straightens out & pulls the pin out of the breakaway switch. If the breakaway battery is charged, the pulled pin sets the brakes on the trailer and stops it from rolling with your precious cargo in it. Depending on how charged the battery is, the brakes will set for up to 20 minutes, which gives you time to chock the trailer tires. But, if the battery is not charged, the trailer wheels may continue rolling and disaster may follow. The battery is usually located in a box at the front of the trailer or in the tack room. Nowadays, to keep it from being stolen, we usually have the battery box locked & it is a hassle to check it. This small replacement switch fixes that problem & gives you peace of mind. Just glance at the switch & make sure the LED light is on at the time of your pre-trip check.