Lufft certified thermohygrometer Model #169 has a 6" dia. overall case of solid brass that is drilled for wall mounting. The 5" dial has a glass cover. The dial face is black with white figures. Model #024 is the same as Model #169 except the dial face is silver with black figures. Both instruments have a Durotherm element that is accurate within ±3% RH. The dial indicates the complete range of 0 to 100% relative humidity. Humidity graduations are in 1% RH. The bi-metallic thermometer is accurate to ±2°F with a range of -10°F to 190°F. Temperature is in graduations of 2°F.