Explained: The noise low - strength is strong, works for 8 hours not to give off heat - the special steel quality of material lightly, thermostable, the plasticity to be strong, and the antimagnetic ability strong characteristic, causes a model community machine stabler work, specialized model community teacher first choice: Frequency 25000 revolutions of - - 30000 revolution of 1 minute Operating instructions: Starts 5V 7-9V normally the normal work.