These pouches do not mount to a belt. These have a PALS/Molle attachment.
The below answer is incorrect. While it may not be designed to attach to a belt, I ran the molle setup around a standard issue Army rigger belt and it worked great. Got it beneath my carrier and easily accessible. When not wearing my carrier it was just as good. Use the webbing on the back to adjust/tighten and you're good to go. Alternatively, get a belt with molle.