The NF-A14 is a premium quality quiet 140mm fan with a square frame that complies with Noctua's AAO (Advanced Acoustic Optimization) standard. Its square shape and 140mm mounting holes ( 124.5 mm spacing) make it ideal for use on water cooling radiators or as an upgrade for 140mm case fans. Featuring sophisticated aerodynamic design measures such as Flow Acceleration Channels, the NF-A14 further improves the renowned quiet cooling performance of the award-winning NF-P14. The ULN version provides super-slow 800/650rpm speed settings for ultra-low-noise applications and highly noise sensitive users who demand near-silent operation. Its superb running smoothness, reference-class SSO2 bearing and Noctua's trusted premium quality make it an elite choice for the highest demands.