Parachute Bags are the flexible way to pack!
They don't take up a fixed amount of space. You can take extra empty ones when you go on shopping vacations (and bring them back full).
You can use them for carrying dive gear or tools. They are made of heavy (22 oz) canvas and are reinforced with canvas strapping at pressure points. You can put the fixed straps over your shoulder or use optional shoulder straps with the attached "D hooks". The handle strapping wraps completely around the bag - there is no way the handle will come apart from the bag.
They are approximately 24 x 15 x 13 inches.
I have used a couple of different brands of parachute bags, some have brass zippers, some have coil zippers, either type is fine. There is a snapping storm closure which covers the zipper and keep rain or snow from leaking into the bag.
As I mentioned in another review, Eagle Creek Pack-It Cubes work great for organizing your clothes inside of a parachute bag.
The bags are available in Black, Olive, and various Camouflage colors. I find the black color to be very neutral and attractive. They are machine washable (the color may fade a bit, but the fabric strength remains).