Multiple small rune pouches may be bought, but only one small pouch can be used at a time. However, a small rune pouch and a large rune pouch can be used together. In comparison to the large rune pouch from Bounty Hunter, the large pouch holds 3 types of runes instead of 2, can be equipped in the ammo slot, and is tradeable. If the same type of rune is in both pouches and your inventory, the order of runes used first is elemental staves/wands/books > large rune pouch > small rune pouch > inventory > wicked pouch.