Keen is the narrowest string created by String Project. The cobalt-blue exterior hides a very narrow section, 1.18 mms and 1.13 mms, but just as strong as any other. The composition is a concentrated technological blend, a mixture of 5 different materials that make it incredibly solid and reactive after a snapback. With its sensitive and powerful qualities, Keen increases the ability for spinning during the game, creating a natural connection with the ball and multiplied effect of power and rotation.