Valve Spring Tester Style On head Spring Pressure Tested Variable Spring Pressure Range0-600 lbs./in. Quantity Sold individually. These Proform adjustable digital valve spring pressure testers feature a digital gauge and an adjustable base to fit all common aluminum rocker arm lengths and offsets. They display in 5 lb. increments with peak hold and backlighting features. The housing is manufactured from black anodized billet aluminum with a knurled grip area for ease of use. The Proform adjustable digital valve spring pressure testers have a 0-600 lb. measuring range.