Yellow Jacket 78060 Complete Test Kit, 0-35" W.C Sensitive diaphragm gauge calibrated in inches of water column and ounces per square inch Improved lamination strength of diaphragm (bellows) to Brass plate withstands higher over-pressure Tube Nipple for easy connection to system manifold Two gauge ranges available The unique single bellows on Brass plate design replaces the double bellows for a stronger seal that resists greater over-pressure