I do not use the pressure switch I found it just adds too much bulk to the grip. I mounted the hook to the base of the light so all I have to do is rotate the front of the light to cut it on. Its a great light. The price about 70$ including shipping. About the same it would cost me to get a good tac light here.
Its a walther tac light kit it comes with a rail adapter the light batterys rail hooks and 2 switches. The corded switch has a pressure switch that can be placed on the grip the other switch there is a button or you can tighten it to cut it on. Its bright much better than a mag light I do not have any photos but you can do a search on ebay for walther tac light and you should come up with a photo