This is my first review of a product. I bought the Laserlyte Pro from Optics Planet. It arrived 2 days after I ordered it. I shoot a 44 Vaquero in CAS. The adjustment for the barrel diameter is very easy. You tighten the allen screw till you have a very snug fit. I tried a little looser fit but it woulnd't stay centered. The laser fires a short burst every time the trigger is pulled. With this set up I can draw, aim and fire twice at different targets around the room. After about a 1,000 rounds of practice this is really starting to pay off. My aim has improved a lot and the cost over live fire has been substantial. You have to remove the end cap from the laser after each practice so that the batteries last longer. Laserlyte says that you should get about 3,000 fires per set of batteries. This thing works in any caliber from 22 to 45. Hope this helps anyone thinking about this as a training option.