I ordered two of these lights (Z-5) a while ago and was extremely disappointed with the performance.
I mounted one light on a Glock 22 -- the fit to the rail was extremely tight and I spent some time filing/fitting the light on the rail.
I mounted the second light on a Mossberg 590 using a Streamlight mounting adapter. Once again, an extremely tight fight.
On both weapons, the fit was tight enough that considerable force was required to mount both lights, and both hands (and a foot) were required to remove the lights from the rails.
This was not the most disappointing aspect of the lights. Randomly, both of the lights would not activate when the switch was depressed. Usually, a sharp slap was required to get the light to come on. I believe this resulted from a poor fit of the backplate on the light combined with molding flash on the body of the light that prevented the bulb assembly/bezel from completely seating on the body of the light. Because of these manufacturing issues, the electrical contacts were intermittant.
Furthermore, the light would not stay ON under recoil on either the Glock 22 or the Mossberg 590. In fact, on both weapons, the recoil would cause the lights to go off AND NOT COME BACK ON WHEN THE SWITCH WAS DEPRESSED. The remedy to this was to remove the backplate and reseat the batteries.
I compared this behavior to my Streamlight M3 and M6 illuminators and neither of them exhibited either of those characteristics (turning off under recoil, not turning back on).
So, some conclusions:
1. Cheap construction. Poor quality control.
2. Functional issues that could result in severe tactical disadvantage.
3. Bigger than an M3 or X200 so finding holsters is IMPOOSIBLE (outside of custom rigs).
My recommendations: They would work well for airsoft toys, but not for serious fighting weapons. My two units are sitting in a box somewhere if anyone wants them. I'll cut you a hell of a deal!
Jeremy