When great accuracy ( + 3%) is called for, specify the Model 730 Precision Hygrometer. It has a polished brass case (6” dia. x 1 5/8”D) and a 4 3/4” white dial, graduated every 1%. The "Supratherm" synthetic sensor element is very responsive and durable. Three holes in the flange permit easy wall mounting (screws included). Superb quality inside and out! (Matches both the Marine Barometer and Precision Barometer).