when temperatures drop to dangerously low levels, consideration is given to the 5,000+ student walkers. the letters qualify the patients to have the animals in their homes and on airplanes. we do not share this information without your permission. one thing i haven’t mentioned yet turned out to be the most important detail. this device keeps track of the reading and record the reading for future reference. to prevent a hole that can appear in the side of the tooth. otherwise it’s a beautiful model with a reassuringly heavy weight and solid feel. 