Instantly variable jacket temperature, to 200 degrees C, enables programmed drying. Instatherm coated jacket with a viewing strip for monitoring temperatures by means of an adjustable depth thermometer inserted into end, or a thermowell (6-7mm OD) may be substituted for the purpose of employing a thermister, controller probe, etc. The 40/35 joint is PTFE-Clad, the outer member polished, thus avoiding the use of grease. The desiccant tube is improved with joint reversed. The heater operates on AC or DC up to 40v, 3 amps.