If you don't know what "next mode" memory (in flashlights) is, it's the extremely annoying mode system that causes a light to go to the next mode every time you turn it on. I.E.; Turn it off in high mode, it will be in mid or low mode when you turn it back on. Unless you have a good memory, it's a surprise which mode it will be in when you turn it on. Or you have to remember to set it to the mode previous to the one you want the light to start in.