The MANTIS Original, the keychain knife that started the craze. This perfect little dynamo provides all of the essentials, right when you’ll need them. A blade, a bulb, and a bottle opener, right on your keys! Unlike some of the small LED bulbs on the market, we designed the B-3 to allow for replacement batteries. Just one of the many great benefits that MANTIS brings to the industry. The blade is 1” long, and the whole unit is just a little bit larger than a quarter.