In the Kanto league, you will find 8 badges: one for each of the gym leaders in the region. These badges can be found in Pokemon Green, Red, Blue, Yellow, FireRed, and LeafGreen (As well as in the second half of Pokemon Gold, Silver, Crystal, HeartGold, and SoulSilver.)
Each of these badges can be attached to the garment (or corkboard) of your choice, as they have tie-tack pins on the back. Backing options shown in last photo.
They are each about an inch in diameter. Badges are water-resistant, but not entirely water-proof and should not be submerged.
The badges are made of plastic (polystyrene, to be precise) and the tie tacks are brass. The badges are 1/16" thick, about the same as a nickel. They will be shipped in a necklace box to protect them from damage, and for easy storage. This listing is for a full set of 8 badges.