I went to my local gun store and tried a large number of holsters to see what fits and what doesn't.
I ended up buying a De Santis Mini Slide for a Glock 17 and it Fits PERFECTLY! I really like this holster, it puts the weapon right where I want it and holds it tight.
Also, the De Santis S.O.B. for Colt 1911 fit really well, but I didn't like the extreme cant of that holster. De Santis Sky Cop for Glock 17 worked but seemed a bit loose at the barrel end. I found a De Santis thumb break for a 1911 and it did NOT fit. Serpa for the 1911 fits well, but it seemed very bulky to me, not good for concealed carry at all. I suspect that most holsters for full sized 1911's would fit, but not all.
This is one of those things that it makes sense to buy in person where you can actually wear it and know if it fits, if it is comfortable and if the gun is in the position that you wanted. Without trying it out (buying online), you are taking a crap shoot and may or may not like what you get, may end up buying another one later. I thought I liked the Serpa based on the internet, but when I got it in my hands and wore it, it wasn't what I expected.
