I bought the TLR-4 for a full-sized, government style 1911. The 1911 is a SigSauer Scorpion with a rail.
The light attached easily and very securely once I figured out the correct rail key to use. I did not immediately notice there was a proper key for my application and I believe the generic 1913 key did not work and there was a 1911 specific key.
I love how the light has a small toggle switch so that I can use light, laser, or light/laser. This way you're not burning up batteries powering both when you don't need.
The ability to momentarily press the light down or hold it on is really nice as well. The switch for that is a easy to operate rocker switch that straddles the trigger guard. So far it seems a perfect reach with either hand's "trigger" finger to use the momentary-on; however, the hold-on switch is stiff at the moment and requires some force.
I did not have to align the laser once at the range. I pulled my 1911 with it attached out of the case and with a bench rest I put the first 3 shots within the 1" diameter bullseye at 10 yds. Needless to say I am impressed.
The laser was clearly visible at 10 yds at an outdoor range. The day was slightly overcast. I did not try a 25 yd shot, I wish I had.
TL/DR: Just buy it! You'll love it!
Pros: Bright, Dual-function, Various rail keys, Accurate, Momentary-on
Cons: Single color - Black, Tightening screw awkwardly sized, Hold-on position switch is stiff
This review was written in the old system and had content requirements that are different than reviews written today.