I will be the first to say stay away from the Serpa.
Some instructors will not allow its use in their training classes, it has jammed not allowing the gun to be removed, it has been blamed for ND's.
If you can not afford an expensive holster look at the safariland 6377, it is the same price point as the Serpa.
I prefer leather like a Galco Fletch.
I put my Serpas in the bottom of the box about a year ago and won't be using them anymore.