Along with a good belt. You need pant's that fit properly. A lot of people say two inches larger for men's or one dress size for women. (pain in the rear finding pants that fit everywhere but the waist for carry). But I find it really depends on what gun you are carrying. two inches larger for men's pants might not work all that great if you're carrying an ultra compact or something.
When I try on belts, and pants I always try with my gun and holster.
“Every person's life is theirs by right. An individual's life can and must belong only to to himself, not to any society or community, or he is then but a slave.”
“If you are unwilling to defend your right to your own lives, then you are merely like mice trying to argue with owls. You think their ways are wrong. They think you are dinner.”
“Pity for the guilty is treason to the innocent."
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