Description:
Per the JM Custom Kydex website, "Our AIWB (Appendix Inside the Waist Band) holsters are designed to tuck the grip of the pistol into the body, yet still be comfortable to wear all day long. All the edges have been de-horned and the body side edges have been "rolled in" for added comfort and retention. They come with a retention screw so the end user can tighten or loosen retention to suit them, and can be ordered in .080 thick material (standard thickness, great compromise between strength and concealability) or .093 thick material (more durable and slightly more "rigid"). We offer three interchangeable attachment methods, a fixed solid loop in standard or high ride, a fixed split loop in standard or high ride, and adjustable soft loops in standard height only. The AIWB can be ordered with an "extra tuck" option that will help lean the grip into your body and lean the muzzle away, and the sweat guard/body shield can be ordered in full, mid, none, or anything in between." I paid $75 through the JM website for it, and waited about 3 weeks for it.
The holster measures 5.75 inches from bottom to top of sweat guard, 3.25 inches from sight channel to end of trigger guard, 1.75 inches thick, outer edge to outer edge, 1.15 inches clearance from belt to first finger groove on a G19, when holster is sheathed. Glock is exposed roughly 3.5 inches, belt to top most point of grip. (Note that measurements are for the holster setup in the photographed)
Reason for Purchase:
I saw a buddy of mine run this holster at a weekend fun shoot and was told to get this holster to solve all my AIWB needs. I ordered it through JM's webpage which was pretty straight forward. I had selected the option for "extra tuck" and paid the added price for it. I was called by JM two or so weeks later asking me if I really wanted it, I do not remember the reason why he asked, may have been because of the medium guard and something about comfort. I told him make the way he would wear it and in the mail I got a medium guard with no extra tuck, I was also refunded the $10 for the extra tuck since it was not added. This was December of 2013. I have been carrying with this holster when I was not T&E'ing other holsters.
First Opinion:
Out of the box the holster looked a lot smaller than I was used to seeing. The roundness of the holster really stood out as being conducive to appendix carry. It came with a kydex belt 1.5 inch loop. At the time I was wearing a Volund Gear Works Atlas G-Hook belt which was 1.75 inches, so I dumped the kydex loops and put on some pull the dot loops. The holster carries very comfortably, I was able to get a few solid classes in while wearing it, few of them were 14-16hr days and I felt very minimal discomfort even at longer time periods. The single Philips-head screw is for customizing retention setting. It came slightly tighter than I normally carry so I adjusted it and I have not touched it since. 
In the Field:
I carried in this holster this for well over a year with periods in between where I carried other holsters, some of which I reviewed. I found the right setup for me, which was rear sights canted forward towards my center-line, providing a wide area for me to find a master grip, utilizing the two pull the dot soft loops at two different heights.
As you can see from the photos above, the soft loops are setup at different heights creating a slight cant, sights forward.
With the cant forward the holster conceals the G19 very well.
Draw starts.
Clear the gun/holster.
Establish master grip.
Begin the draw.
Gun defeats retention, notice minimal waistband movement between initiation of draw and retention defeat.
Gun clears holster.
Gun presentation initiated.
Gun presented two-handed.
Reholster process started, reverse draw with thumb catching shirt.
Thumb on back-plate, trigger finger out of trigger guard.
Gun holstered by retention.
Draw from the right side, one handed.
Shirt cleared, master grip established.
Defeat retention, upward draw, make note of the belt line movement.
Cant gun forward and move to position.
Presented, cant gun, sights outward, to provide room for function.
Ownership and Usage:
Two specific gripes with this holster. First is that it does not accept Glock 17's, 17L's or 34's. I prefer holsters that will allow multiple designs of 9mm Glock's to fit them, but that is not a big issue and the fact that the end part (under the barrel) is rounded for comfort it may be a design feature. Second is an issue that plagues all AIWB holsters, doing any type of prone work (laying on your stomach) with a rifle or just laying on your stomach. The holster does conceal well and is very comfortable. It has a slightly smaller footprint than a DarkStarGear AIWB and bulges slightly more than the #wulfburht AIWB prototype holster I ran for a while. This holster is not just very comfortable it allowed me to have a consistent draw position which allowed me to make very consistent sub 1 second draw shots in the high .9x range. If I could change or "fix" anything on this holster it would be a more low profile clip/loop setup that allowed the cant I want and for a cleaner bulge. I did multiple combatives, hand to hand, CQB and other type training wearing this holster and it never gave me any issues. The gun never fell out while I was rolling around and it always allowed for an easy deployment while maintaining steady retention.
Final recommendations:
I am not getting rid of this holster any time soon. The price is slightly above others in the business, but it is totally worth the extra ten or twenty bucks to get the features and setup you want. Other holsters to consider are the DarkStarGear AIWB I mentioned above and if you want to spend more getting a custom holster from #wulfburht. I would say that if you are looking for a no-BS AIWB holster with a fair amount of adjustment and customization, this is probably one you should try in your journey to find the perfect one. Specifically consider carrying it directly in front your inguinal crease to take complete advantage of the holster's design.