I live in GA and sweat alot while working. I had the inexpensive Galco IWB holster for my MK40 and every day after work I have to mop off my gun and let the holster dry over night. Read that this way, after work there would always be water(corrosive salt-water a.k.a. sweat) standing and dripping off my gun.
Yesterday, I got my Blade-tech IWB Concealex(platstic) holster, $55. So far it is really comfortable, and super easy to draw from. I'll know more come next week when I am at work and sweating. However, I always wear a shirt between me and my holster, so that helps with the comfort factor.
Maybe an equally priced leather holster would hold up, but with the way I sweat it would be soaked at the end of every day.
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Know Yourself, Know Your Weapon, Know Your Enemy; then Know Victory! ---DaHaMac