Cardsharp Black Credit Card Folding Razor Sharp Wallet Knife Safety Tool. Ultra Slim - Folds to the size of a credit card, 2mm thin! A protective sheath material with high quality plastic Folds to the size of a credit card, 2mm thin 100% brand new ultra thin item Surgical Steel Blade - Stainless steel construction for durable, rust-free sharpness Easier to open than ordinary penknives, and no metal hinges that rust.