Breakaway Switch

There are two types of breakaway switches. One without the battery, which you want, because you have a battery already on the TT. The other type of breakway switch that includes a battery and box are for those trailers that don't normally have a battery such as utility trailers, horse trailers, & stock trailers. The breakaway switches for those trailers have a small battery box and battery included. The box is approx 6" X 6"X 6". Napa sells both because they are vehicle parts dealers. The Napa guy was leaving the choice up to you. RV dealers only sell one type because they deal mostly with RVs. Hope that clears it up. Doubt he needs to go back to school for selling both types. Many people don't realize there are two types.