These 5"x 7" sticker cards are almost a large as an adult-sized hand, and fit comfortably into 2-pocket pages as shown below. Packs of GS1 originally contained 3 different sticker cards with the set checklist located on the back of the pack wrapper.
The major variation that I'm aware of for this set is with it's greatest Hall-of-Fame character, Adam Bomb, which has 2 different back variations. Adding the Adam Bomb back variation to you set turns it into a 40 card set that will completely fill 20 pages. If you want to add a wrapper to the front and back of the set, it will fill 21 pages.
This set is a larger-than-life version of one of the most famous GPK sets of all-time. Almost 4 regular-sized cards could fit inside one of these. Why wouldn't you want to include this monster into your collection?