Here is my pic of the two side by side. The big pocket is MUCH bigger, with wraparound straps and a full-front pocket (length-wise). The medium pocket has side buckles going vertically, and a smaller front pocket. The big pocket is about 18" wide (when smooshy...Chloe lists it as 15") by about 10" tall by about 8" deep. The medium is about 14-15" wide by about 8" tall by about 6-7" deep.