If it's the one I'm thinking about, there is a wire ring that fits the grooves on the inside of the light. You need to pinch the wire ends together, which pulls in three areas that have wire extending into slots on the inside of the light. Once you've pulled the wire out of the grooves, simply pull the head off the light. It's not quite that simple, as you need three hands to do it, so put it between your knees and hold it with the knees, pinch the wires together, and pull the top off the light. Everything works on friction, but not too well. Turning on the light by rotating the head works, but turning it off doesn't work too well. This is because on the inside there is a not-so-cleaver travel pins which must go "uphill" to turn the light off. I never liked these lights, if it is the one I'm thinking about.