OAKTON® Three-Speed Battery Operated Hygrothermograph will safeguard areas where it is vital to maintain adequate climate control. Unit has accurate quartz-controlled drive mechanisms that consistently rotate chart drums, even when batteries are weak. Battery Operated Hygrothermograph includes everything you need to get started: two felt-tip pens (one blue, one red) and one seven-day sheet of chart paper and a roll of one-month paper. Allows you to choose from from 1-, 7- or 32-day operation with the flip of a switch. Works well in indoor or sheltered outdoor environments such as storage or agriculture areas. Features single button battery condition tester and flashing LED which indicates that unit is operational. Runs on two C batteries (included) for up to six months. 13-1/4" x 11-1/2" x 5-1/8".