Durable, Dependable, High Value Auto Levels-3 Models - 32x, 28x, and 24x Magnifications,Rapid, Accurate, and Stable Automatic Compensation,Ultra-Short 20cm (7.9 in.) Focusing,All-Weather Dependability,Clampless, Endless Fine Horizontal Adjustments , Rapid, Stable, and Durable CompensatorThe compensator of B20/B30A/B40A incorporates four suspension wires made of super-high-tensile metal that features minimal thermal expansion coefficient, providing unmatched durability and accuracy. Finely tuned magnetic damping system quickly levels and stabilizes the line of sight despite the fine vibrations present when working near heavy equipment or busy roadways.