Fan of Japan? This is the official currency of Japan. Unrelatedly, yen is a slang term meaning a strong craving, desire, or yearning. Moon Wallets are slim, double laminated, made out of 115gsm couché paper, can easily fold, eco-friendly, vegan, waterproof, and have 7 slit pockets for your credit cards. Moon Wallets is a great alternative to old-fashioned bulky wallets and a conversation piece. Our Wallets are a 2.75" x 3.75", standard wallet size.