After reading good reviews about EL530 lights I bought an EL500 as I was told that it had longer battery life for only a slight reduction in intensity. The light performed well until I failed to fit it properly onto the mount and it fell to the floor. The light stayed on so it wasn't til the end of the ride that I found it would not turn off. Rather than look stupid in the pub I removed the batteries only to find that it would not go on again when I replaced the batteries. I have since taken the thing apart and found a small printed circuit board and what I think is called a reed switch contained in a small glass phial. Needless to say, this was broken. Cateye have gone to great lengths to make this unit waterproof but have failed to make it shockproof so, if you have one, be very careful. If you were thinking of getting one, bear this in mind. I'm pretty sure the EL530 has the same switch.