With added option, exposed calibration on top of Therma Gauge is available in all glass, making gauge more durable when it is outside and exposed to elements. Glass gauge will withstand virtually any amount of sun exposure and heat, replacing cracked, cloudy, warped, or discolored plastic tops. Solid Glass Calibration can be ordered as add-on option for new gauges or as Solid Glass Repair Kit to upgrade current gauge in field.