Grey has a sleek white and silver zipper, clear buckle, pocket at the back for small accessories and a lined interior with a pocket. 
 
Model is wearing a small. 
 
Grey pack is available in the following sizes:
Small 10.75" Long x 6" Tall x 2" Width 
Medium 14.5" Long x 6.25" Tall x 2.25" Width
Large 15" Long x 6.75" Tall x 2.25" Width
See Harlee packs here for size differences.