Product material: aluminum alloy Product size: 3.3 * 2.7 * 9.8cm / 1.3 * 1.1 * 3.9in Use battery: 3 AAA batteries / 3 x AAA batteries (not included) Light source: red LED lamp beads Working voltage: 4.5V Instructions: Step 1 Dim the lights as much as possible. The dark room will show the best results. Press the button on the bottom of the device to turn on the light. Step 2 Use light to gently apply pressure on the skin, and then slowly move the device left and right. These veins will appear as shadows or dark lines and appear in the red glowing periphery seen around the device. Step 3 After finding the vein (shadow/line), reposition the light around the area to best see the vein. ★ I am very happy that you can visit my shop, I wish you a one-stop shopping, happy shopping!