X-Fan 40 x 40 x 20mm DC Axial Fans 5V/12V, Ball/Sleeve Bearing – X-Fan RDM4020B1, RDM4020B1 is a high-quality ball bearing 12V DC axial fan from X-Fan which has been manufactured to a high standard. Both lightweight and small, this brushless cooling fan has passed through stringent quality control testing. X-Fan RDM4020B1 40 x 40 x 20mm Axial Fan 12V Ball Bearing