X fan 40 x 40 x 20mm dc axial fans 5v12v ballsleeve 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 and has the following safety approvals x fan rdm4020b1 40 x 40 x 20mm axial fan 12v ball bearing