This is a flattened Flintstones 1994 Post Cocoa Pebbles cereal box.  The front of the box pictures Fred Flintstone eating Cocoa Pebbles while Barney Rubble is sneaking some out of the side of the bowl.  The bottom corner has a banner which says "Free with proofs-of-purchase Stone Age Stuff from the Pebbles Bedrock Shop".  One of the side panels has the mail-in form to order from the Bedrock Shop.  The back of the cereal box pictures the 6 different items that were available along with the number of proofs of purchase needed.  This is a 17 oz cereal box.  When assembled , the box would measure approximately 8" x  11 3/4" x 2 1/2".