How to Use: 1. Insert the battery (battery purchased separately). 2. Remove the receiver, insert the USB port of the computer and other equipment, the receiver will be installed automatically. 3. Start to use after pairing successfully. Specification: Item Type: Wireless Calculator Material: ABS Product Size: Approx. 140x83x26mm / 5.5x3.3x1.0in Connection Method: USB connection Number of Keys: 20 keys Support System: For Windows XP/win7/win8/win10 Transmission Distance: 6-10m / 19.7-32.8ft Keyboard Battery: 1xAAA battery (not included) Package List: 1 x Manual 1 x Receiver 1 x Wireless Numeric Keyboard(Battery Not Included) Note: 1. Please allow 1?2cm error due to manual measurement. Thanks for your understanding. 2. Monitors are not calibrated same, item color displayed in photos may be showing slightly different from the real object. Please take the real one as standard.