Notes: We are one of the earliest manufacturers to modify metal jet fans. Please believe that this 40mm jet fan we sell has the best cost-effectiveness. Jet fans have extremely high speeds and high power. Please do not test without protective measures. After exceeding 100,000rpm, the heat rise . Please do not work at the highest speed for a long time. You can reduce the voltage to prevent reaching the highest speed, or use the controller to slightly reduce the speed. Warm Tips: 1. Do not stand directly in front of or behind the fan. The jet fan may be and eject high-speed fragments by sucking in debris. Some videos on the Internet may make dangerous moves to show the power of the jet fan. Please do not imitate. 2. Aluminum alloy shell, heavy weight, although the thrust is large, but not suitable for use on model aircraft, can be used for DIY enthusiasts and other purposes Colour:Silver Material:aluminium alloy Package Contents: 1 * 160000 rpm DC brushless motor Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.