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., Manufacturer: PokFhgur