This is our top-of-the-line angle meter, quality is unparalleled. A hold button freezes the reading on the display for hard to see measurements. Zero can be reset to any angle which provides for quick measurement comparisons. This "alternate zero" function also makes it easy to copy any angle setting for things like rafters, handrails, or items that need to be made parallel. The patented, easy, one button calibration resets accuracy to factory specifications with no special tools on any relatively level surface. Many uses including instant, accurate measurement of burn test required angles. It's small, light weight design is perfect for using in tight spaces. The rugged integral aluminum frame assures a product that will provide years of trouble free service. The Pro 360 ships with a 1 year warranty and a 9 volt battery in a hard plastic carrying case. It feels good knowing you have the best, the original Pro 360 Digital Protractor. Donít accept knockoffs using this same model number - - buy from ED&D!