I bought a double mag holder. Oddly, one pouch fit perfectly but the other pouch's opening was a bit small in the inside corners, even after loosening the adjustable tension ****. With a Dremel tool and grinder attachment, I thinned-out the thickness of the Kydex material from the inside of the pouch's corners outward, thus allowing the four corners of the spare mag to more easily slip into the pouch. Problem solved. Great-looking Hawaiian Red to match my Hawaiian Red TEOTWAWKI holster for Springfield XD-M 3.8" 10mm.
