Are you going to be mounting it on a Jennings handgun or a real gun? If you have a real gun, get a real light.
Streamlight or the Surefire. The Surefire is several times more expensive than the Streamlight. I have the older Streamlight M3, no laser, dual 123 battery, xenon lamp. Works great, very bright. Very reliable.
Spend the extra bucks on this. Get good ammo too. Corbon, Gold Dots, BuffalloBore, Double Tap, etc.