Vaisala HUMICAPr sensors have excellent accuracy and long-term stability, negligible hysteresis, and resistance to dust and most chemicals. Two-wire transmitters monitor your humidity or RH/temperature conditions with ±2% RH accuracy. All wall-mount models have ABS plastic housing; duct-mount models have aluminum housing. Probe on models 03334-18 and -36 measures 3''L x 0.75'' dia. Sensors on models 03334-15, -18, -35, and -36 include a 0.5-µm membrane filter.