I've used a competitor's ankle holster for years for my bug. It didn't have a retention strap, and the first time I wore it, I had to run up a short flight of stairs to rescue a family from a burning house; the Makarov I carried fell out. That holster would only stay in place when I wore it atop my combat boots; in regular shoes, it would slip down below my cuff. This holster with its above-calf strap did not slide down even a quarter of an inch. I carry a Beretta Tomcat in it, and it's not only secure, it is so comfortable and light I forget I am wearing it. And, it solves my problem of how to have my CCW on me, in my control, and easily retrieved while driving. I wear it on the outside of my right leg, within easy grasp if I ever need it in a hurry.

Only been wearing it for about a week, but very comfortable. My Taurus G3C fits in it, but with the standard finger extension mags, and slim fit boot cut jeans (not skinny jeans just the middle ground between baggy and skinny in the leg) it prints pretty bad.
That isnt the holsters fault at all, just a heads up to anyone considering this holster. Ill try it again once i get a more subcompact/slim 9mm or flush fit mags.
For now i am using it to hold a TQ, leatherman or spare mag in the smaller pocket, and Quickclot or a pouch of ETD in the "gun" pocket. Depends on my environment that day.
I personally think its a better option than the $50 ankle med kits, because the top strap holds the weight of your kit on your calf, and its more comfortable than the standard ankle med kits. I also wear cowboy boots so the pocket area stays very secure. But i think with two straps it will stay in place even with shoes or regular boots.
Highly recommend this product

Comfortable supportive secure and breathable

I haven't used it yet, I don't yet have a CCL but it looks like it will do what I want.

I bought this over a year ago. I wear it daily M-F for 8-10 hours a day. The velcro still holds. The strap and buckle still works. Good retention for a smaller framed pistol (Bodyguard .380). It conceals well, and is easily accessible, well as accessible as an ankle holster can be. The only negative is the spare magazine carrier strap is waaaay too big. The carrier holds the magazine but it may fall out should you take it out and hold it upside down or do cartwheels. I have never had a magazine fall out while wearing it though. My fat ass hasn't done a cartwheel in decades.