HB-21 BEARING SENSORHB21 The HB21 Bearing Temperature Sensor screws in to replace an existing grease fitting. Allows continued greasing of the bearing. CSA Certified Class II, Division 1, Groups E,F,G 1 8 and 1 4 NPT sizes Fully adjustable length. Base lengths available: 3, 4. 5 and 6 Available in the following sensor types: Thermocouple: Type T and J RTD: PT100 Digital: 1 Wire Not sure which insert length you need? Check out the selection chart photo for guidance.