They turn off and on by passing by a magnet, like someone else said. Not sure why you would want to leave it on...it comes on when you shoot it.

I have two packs of Tracers that I am going to put in the classifieds if you are interested. New and still in the package. you can pm me if you are interested. They are for alums and beman carbon hunters and I don't shoot either anymore.

The Tracers are no doubt a better choice then Lumenocks, but I prefer the new Firenocks over any of them.