Q: "DC Fan" 4010, 8025,12025 are a fan of the aircraft, said life, how they are named. A: usually a fan shape according to its size named. 4010: L = 40MM; W = 40MM; H = 10MM. 12025: L = 120MM; W = 120MM; H = 25MM. Q: fan models by institutions is how to divide? A: usually the fan axis is structured into one ball one sleeve: a Peilin Jia a coaxial, prices generally, long life; two ball: two Peilin more expensive, longer life; sleeve: cheaper copper price axis , short life. Q: Fans are usually external PIN lines are there? A: usually in line then divided 2PIN, 3PIN, 4PIN. 2PIN: VCC + GND; 3PIN: VCC + GND + FG / VCC + GND + RD; 4PIN: VCC + GND + FG + PWM / VCC + GND + RD + PWM.