Backer Marathon offers Fixed Melt Bolt Thermocouples. Mineral Insulated Thermocouples are manufactured at Backer Marathon to address your higher temperature requirements. Since the calibration wire is encased within a metal sheath packed with magnesium oxide the thermocouples can withstand higher temperatures and depending on the application will last longer since they are more durable. One excellent feature of Mineral Insulated Thermocouples is faster response time. We stock hundreds of different models and offer quick turnaround, usually 48 hours or less, on custom designed and manufactured units.