I have one on the Solo CDP and the G27. They’s not very accurate very far out past 30 feet or so, just good for close quarters.
I have ‘em on several Class III firearms, but the red lasers wash-out in bright sunlight. They’re best at dusk, night or early morning. With a good piece of glass, I can see a 635mW (Class IIIa) green laser out to 200yds, in daylight. Haven’t tried the Class IIIa/b blue, purple or yellow units yet:
http://www.laserglow.com/int-handheld.htm?gclid=CMW3ntya6LECFUJx4AodDE4A_A
At night, inside a house with an intruder, putting a laser dot on his chest, can make him soil himself. It’s almost as good as racking-the-slide on a Remy 870 pump.