SENTINEL™ Source Guide Tubes are flexible stainless steel tubes with a protective polyvinyl covering and are available to fit all SENTINEL gamma-ray source projectors. The Extreme Condition Source Guide Tubes are designed for use in extreme weather conditions. They have a temperature range of -60 to 135°C (-76 to 275°F). All Guide Tubes and Extensions are a standard length of 7 ft (2.1 m). Custom lengths are available upon request.