The DYMO M10 digital letter scale weighs envelopes and packages up to 4.5 kg. Connect via USB to a PC or Mac® to use with popular online mail and shipping software - including Endicia® InstaRate and DYMO Stamps®Software and calculate and purchase USPS®-approved postage online without monthly fees. Convenient features include a "hold"... function that displays the weight for ten seconds, an empty weight function (tare) for accurately weighing items in a container, an automatic shut-off and an LCD screen that displays the weight in an easy-to-read digital format - in lb/oz or kg/g. The unit is powered by USB cable (supplied) or 3 AAA batteries (not supplied).