Pocket measures approx. 2” x 4” and has hook and loop closure.
I originally designed them to hold extra memory cards, debit/credit card, business cards, cash, maybe a lens cloth……..anything small and no thicker than about ¼” but a lot of people use it for their cap. Most batteries are a little too thick to fit.
The largest cap it will hold is 58mm. Strap is 2” wide, a 58mm cap measures 2 ¼” so it is a little wider than the strap, there is enough hook and loop to allow the flap to close.
Nature/Wildlife Photographers: hook and loop is LOUD! Especially when you’re trying to be quiet ;-)