I actually just sold mine on ebay. I had the Ruger SR9 Viridian Laser, which worked great.
It fit on my sr9 and my glock 21
I would take the Viridian green over a red laser any day. It shows up really well when using it in the daylight or a well light room.
The laser has multiple settings from a constant light beam to pulsating beams.
It is a little bulky, but not horrible for a rail laser.
When I purchased my SR9 it came with a special offer for the laser & BlackHawk holster that fit both, for a discounted price.
I was however disappointed with the holster that was made of "nylon". When the gun was in the holster with the laser, it would turn on easily because of the location of the on-buttons.
If your looking for a laser, I would definitely go with the Viridian brand, and if you were going to get a holster for both, I would stick with a hard plastic type (Kydex).
Hope this helps