I like this one on my wood stocked rifles. It's big enough to carry car keys, 5 rounds of ammo, cell phone, 25' of parachute cord, small cleaning kit and a Snickers bar.
This is the one for serious hunts at least 100 yards from the truck. I can carry a full box of ammo, keys, cell phone, rope, knife, cleaning kit, rubber gloves, a bag of chips, toilet paper and 2 meatloaf sandwiches.
I'm working on making one with an aluminum frame so I can carry out a deer hind quarter on my butt stock.