The Ninja Knife from Wallet Ninja is a compact folding knife with the length and width of a credit card. Slip this useful tool into your wallet and you can always have a knife at the ready. The 3" blade is made from surgical stainless steel and features a gray heat treated finish and a razor sharp edge. With three easy steps the Ninja Knife folds from the closed to open position in seconds. The Ninja Knife is far less bulky than a traditional pocketknife and just as easy to use.