50# USB Digital Shipping Scale Integrated with stamps.com software for Microsoft Windows and MAC (OS 10 or up) Capacity: 50lb/ 23 kg; Weighing Mode: lb-oz/ lb/ kg-g; Readability: 0.1oz/ 0.1lb/ 5g TARE function covers unit's full capacity range Flip-up platform can hold large envelopes Powered by USB port or 9V battery (included)