Amazfit T-Rex Pro is considered to be the most affordable Military Certified Rugged Outdoor Smartwatch. Passed 15 regulations of military standard (MIL-STD-810).Extreme Temperature and conditions from 70C heat to -40 cold along with 240Hrs of humidity, 96 Hrs of Salt spray and many more. Size: 4.8 x 4.8 x 1.4 cm