Spectra Products’ Hub Alert is a heat sensing label that functions as an early warning system to alert drivers and maintenance personnel to above normal wheel end operating temperature. This normal operating temperature of wheel hub oil or grease should not exceed 225ºF. Wheel end manufacturers recommend a detailed inspection if temperatures reach 250ºF to address potential seal and bearing problems. The Hub Alert will turn black permanently when the temperature reaches 250ºF, alerting that further inspection is required. After inspection, a new Hub Alert label is applied to the wheel hub to continue the early warning temperature alert. The Hub Alert thermosensitive area is hermetically sealed against moisture, oil, grease, fuels, water and steam.