Resistance thermometers usually consist of a ceramic or glass core, containing a length of fine platinum, nickel or copper wire. Since resistance thermometers are fragile, they usually come in a housing or with a protective pocket. The common accessories bought along with resistance thermometers include immersion sleeves and tension straps. These thermometers are now in widespread use for industrial applications, for measuring temperatures below 600°C. Miniature temperature sensors are resistance thermometers that fit almost anywhere, and are waterproof. These sensors are flexible, with very small diameters, and ideally suited to pharma, biotech, sanitary and industrial process applications. These devices usually have an operating temperature range between -200°C and 200°C. Thermometers are available in various measuring ranges, measuring element, lead and output. Depending on the application, the sensitive length and wire configurations may also be important considerations. A thermostat, in contrast, senses the temperature of a system, to maintain it at the desired point. When the device is hotter or cooler than the set point, the thermostat switches on the cooling or heating mechanism. Thermostats come in various switching temperature and reset temperature modes, and may require accessories such as mounting clips. The usual operating temperature range for thermostats is between – 55°C and 160°C.