This flap was designed to be a very versatile option that is compatible with most Velcro lined mag pouches on the market today. 
Ultra secure retention due to the buckle, but once the buckle is undone, the flap is very quick and easy to use due to a small piece of hook Velcro (the grabby stuff) on the front of the flap. It’s really the best of both worlds. Easy to access when the buckle is defeated, but still plenty of retention. 
Compatibility: 
Requires loop Velcro (the soft stuff) on the inner backside of whatever pouch you’re putting it on, and at least 4” worth of Velcro loop on the front of the pouch. 
These flaps will work with our RECCE chest rig, Split Front Chest Rig, Micro Chassis, Macro Expanders, Surus Double AR Mag Pouch, and Mission Driven Chassis.