Those Chinese motion sensored lights are screw in attached and USB charged. So order the seat rail mount and unscrew the mounting kit, then screw the mount on your trailer end. I did that with my racks, but felt it wasn't bright enough for riding at night, AND it's a throwaway once the battery is dead, which mine did after 1.5 years. I went with a Cygolite 350 as a replacement, which my battery guy has told me he can definitely replace the liPo battery vs those little motion lights (I bought Meroca, but they have OEM for many different brands).