The listing, Calculator has ended.
Totally Flexible Rubber Pad, see the electronic paths, and the clear back panel shows the board and battery. Takes one AG7 battery. This has the advantage of not sliding around on surfaces as you work, and is fairly water proof at least from the front. Sealed with some tape on the back to further protect that and you are good to go anywhere in any weather. 6 inches by 3 3/4 inches and 1/4 inch thick.