Product review (5 stars): Its a refill - Just the bag to go in the box you already have
The refill comes in a bag just like the first product you bought which was in the box as well.  The refill replaces the bag in the box.  If you don't already have a box, why would you buy a refill?  You wouldn't buy refills for a pen that you don't have.  The product is great and saves money over purchasing regular stuff.