These mystery packs have been popular at comic conventions so they are now availble in the online shop as well. They can include anything - prints, doodles, booklets, stickers, postcards, pins, etc. They are usually good value for money. 
 
Three sizes available. 
 
Small: Contains 3 - 4 products
Medium: Contains 4 - 6 products
Large: Contains 5 - 7 products