the one on NM is the medium and it retails at $1620
the big is much bigger and i think NAP has a picture of it so check it out there i think it sells for around 1850
i dont have the dimensions tho...but the check around the threads im pretty sure someone posted it. if you do a search for ETenebris she has a picture with a comparison of her large and medium pocket. hope this helps !
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.