Thermocouple Protection Tubes One End Closed for use up to 1800.Grades: - 60% Al2O3, 80% Al2O3, 90% Al2O3, 99.5% Al2O3.Size(O.D) - from 6mm OD to 44mm OD.Lengths - up to 1500 mm regular size- up to 2000 mm on request.Uses - Protective Tube for Thermocouple sensors.