Pulley PRO® uses a green laser beam and magnetically attaches to the inside or outside face of any pulley or sprocket. The product uses reflected laser beam technology for maximum angular resolution and can measure spans up to 15 feet with any size pulley. A laser line is projected from the transmitter to the reflector mounted on the opposite pulley. A reference line on the reflector indicates offset and vertical angle misalignment. The laser line is then automatically reflected back to the transmitter's reference line to show horizontal angle misalignment.