Depends on the mags... I had to sell some metal LAR mags because the cutout for the mag release would bite into the KYWI like a cheese grater and hold tight.
If all else fails you can spray a little Armour All onto a cloth and wipe it on the inside of the KYWI to slick it up some.
That said, I love the Esstac KYWI mag pouches and won't use others!!!!!!