The Viper Tec Don is a one of a kind switchblade and OTF all in one! The Don OTF is a stylish automatic knife from Viper Tec Knives. This Italian style made automatic knife features a double-action firing mechanism. You simply slide the front-loaded button forward to activate the blade, and pull it back to retract the blade back into the handle. The Concord's are perfect for collecting or light cutting chores.