Keson MP401E Electronic Metal Frame Measuring Wheel with Spoked Wheel, 15-1/2-Inch Diameter Swan-Neck ergonomic handle. our patent-pending thumb-up grip ensures less wrist strain and superior control Dust, dirt and other particles can disrupt a light beam used in competitive units, our magnetic pick-up avoids these problems Sealed counter encasement Counter size and placement Calculates area, and stores readings in 8 memory storage fields