Large, easy-to-read 3-1/8" (80 mm) steel case red and blue, 1% accuracy (Class l) gauges, front access for easy field recalibration, optional protective gauge boots available Proven, double "O"-ring piston for reliability and long service life Exclusive 100 mesh filter in-line on all flare fittings helps keep out particulate material and extend the life of the seats Sight glass to easily view refrigerant movement and condition during charging and recovery Heavy duty hook won't pull out