Corn Bags/Flour Bags
Heavy Duty Brown Kraft block bottomed bags originally used for fixed weights of corn and flour (which is why they are still referred to by their weight capacity) but now used for any application that requires a strong paper bag.
Note that while the base of these flour bags is flat and rectangular (the size of the base is obtained from the first and last measurement), the sides of the bag have no side pleats. The height of the bag is shown as the second measurement. Flour bags are wider and shorter than their ‘Kraftex’ equivalents (see further down)

Kraftex Bags/American Shopping Bags
Heavy Duty Brown Kraft block bottomed bags, very similar to our corn bags/flour bags (see above) but these bags have side pleats and are not as heavy quality paper as the corn bags. The middle size refers to the width of the bag with the pleats fully opened out. These bags are taller and narrower than the Flour Bags shown above. These bags are often seen in American TV shows being used as shopping bags