Our 4120WBL mechanical boom angle inclinometer is a -30 to +90 degrees unit with 5 degree increments. The housing is made of rugged thermoplastic making these clinometers extremely tough for all types of environments and weather conditions. With operating temperature ranging from -50°F to 180°F the 4120 is the perfect all-season boom angle indicator. The large, clear number and degree markings make it easy to get quick, accurate readings.