All petur piezometer designs use the basic Petur Pneumatic Piezometer Sensor. This Paatent-Pending design is based on more than 10 years of development and refinement and we believe, is the finest, most reliable pneumatic sensor available anywheere. It is no-metallic and is corrosion free, both internally and externally, and has no moving mechanical valve assemblies that will stick, jam or corrode. See specifications on back page.