Wire strands can be built up with concentric helical layers of wires of the same diameter. For example: 1+6+12+18+…. The longitudinal distance along the strand required for one complete helical wrap is known as the lay length. Each layer can be wound in one of two directions: left, also called ; or right, also called . Subsequent layers can have the same or opposite directions. Lay length and direction are important design parameters that affect both the strength and flexibility of the strands.