Charlie says... These are damned hamdy. The bent one is for frame with a little tube linkingb the seat tube to the top tube, such as a Surly Ice Cream Truck... etc
The Jerrycan® is a small rear mount specific bag to max out your carrying space. It's narrow, only 2" wide, so your legs don't hit it when peddaling. Good for carrying some spares, tools, or some food.
Constructed with VX 21 fabric, padded ballistics nylon along the tube sections, yellow interior, Plastic HD side panel inserts, #5 YKK water resistant zipper, interior elastic keeps a multitool from rattling.
There are two Jerrycan models:
Regular - For most bikes, the seat post / top tube angle is slightly obtuse to fit lots of frames. If your bike has an acute angle there ( really sloping, dropped top tube) then it will just be pushed foreword a bit and take up more real estate along the top tube.
Bent - For bikes with gusseted braces at the seat tube/ top tube junction.
Note - These bags are rear mount specific, they will only work up front if you have a lot of spacers under your stem.