Amprobe AC40B Clamp Type Digital Multimeter Power Supply: Two (2) 1.5 V AAA batteries (UM-4) Maximum Jaw Opening: 25.4 mm Operating Temperature: 0 C to + 40 C, &lt; 80 % R.H. noncondensing Storage Temperature: - 10 C to + 60 C, &lt; 70 % R.H. non-condensing batteries removed Battery Life: Alkaline 300 hours, approx.