1 custom made box protector for the smaller Pokemon Booster boxes like the ones pictured.  These do work with sealed boxes!   

These do not fit all booster boxes.  They do not fit Sun and Moon or the original booster boxes and there could be others that don't fit too.     

These protectors are 5 3/8 x 4 7/8 x 2 3/4.   If your box is bigger than 2 3/4 you probably need the large size instead of the small.   

14mil PET Acid-Free plastic

Removable Peel Film