The PERFOtronic automatically measures by rounding up or down to the next 1/4 perforation shown in stamp catalogs. The processor of the unit is able to calculate around missing perforations or perforation mistakes. Measures the perf. value within a fraction of a second with the help of light sensors. Nothing touches your stamp, therefore no damage possible. Accurate to 1/100 mm. Displays in 1/4 increments, i.e. 14.25,14.5, 14.75, 15, etc. Operates on an AC adapter with 12 Volt DC output (supplied). Use on regular or large stamps, coils and stamps with margins. Maintenance free. Size: 7-1/2"x 5-1/2" x 2-1/2" High.