Incandescent trailer light bulbs corrode, break, burn out and fail at a discouraging rate - even on sealed beam lights. LED lights, like these from Optronics, Inc., draw fewer amps and are brighter than bulbs. Each sealed unit has the most vulnerable connections protected inside the bezels, making them impervious to fresh or salt water. Sizes and shapes fit most trailers, and the left tail light features a license plate illuminator as well. These are the first upgrade you should make to your trailer. From $69.95; www.overtons.com.