Noctua offers a wide selection of fans for various demands and purposes. Use the following criteria to select the model that works best for you:

1. Size and shape: The first thing you should determine is what size and shape of fan you need. For example, you might need a 120mm size fan for your water cooling radiator vs a 40mm size fan for your router. Note that for some sizes there are different shapes (e.g. square frame and round frame for 140mm size) and depths (e.g. 25mm and 15mm for 120mm size, 20mm and 10mm for 40mm size, etc.) available, so also check which shape and depth is required (e.g. round frame fans for most 140mm CPU coolers vs square frame fans for most 140mm water cooling radiators). If you have enough space, always choose the bigger depth fan (e.g. 120x25mm rather than 120x15mm) for the best possible performance.
2. Voltage: Most Noctua fans are 12V, which is the standard for PC applications. Note, though, that there are also 5V and 24V models available for other applications. The latter can easily be recognised by the "5V", "24V" or "industrialPPC-24V" designations.
   We offer the NA-VC1 step-down voltage converter to use our 12V fans in 24V applications.
3. Product line and colour scheme: In addition to the standard line of premium-quality quiet fans that is easily recognisable by the signature brown colour scheme, Noctua offers 3 dedicated product lines for specific demands:
   • redux: streamlined, more affordable packages for price-conscious users, grey colour scheme
   • chromax: black fans with swappable anti-vibration pads in various colours, ideal for coordinating the fans with individual build colour scheme
   • industrialPPC: ruggedised high-speed versions for challenging environments, black colour scheme
4. Connector: Noctua fans are available with standard 3-pin and 4-pin PWM connectors. The latter can be identified by the “PWM” designation. Choose 4-pin PWM versions if you would like to use the PWM fan speed control of your motherboard (or other devices). The 3-pin versions can only be speed-controlled by reducing the voltage (or using the supplied Low-Noise Adaptors in the case of FLX and ULN versions). However, as explained in this FAQ, 3-pin fans can also be used on most 4-pin headers and vice versa. Note that some models also come with adaptors for 4-pin peripheral connectors, 2-pin or USB connectors, or the OmniJoinTM adaptor set that allows the fan to be connected to proprietary fan headers. Please refer to the specifications of the individual models for details.
5. Noise level and RPM speed: Please refer to the dB(A) specification of each individual model for selecting one that fits your requirements regarding noise and performance. In general, higher RPM speeds result in higher noise levels, but note that the relation of RPM speed and noise differs from fan size to fan size (e.g. a 2000rpm 40mm fan may be quieter than a 1500rpm 120mm fan) and from fan design to fan design (e.g. the NF-S12A 120mm fan at 1200rpm is quieter than the NF-F12 120mm fan at 1200rpm), so always refer to our dB(A) specifications rather than to RPM speeds only. In the different product lines, we use different designations for highlighting the fans’ speeds and noise levels:
   • standard line: HS-PWM versions are the highest speeds in this line, PWM and FLX versions are high to moderate speeds and ULN versions are the lowest speeds
   • redux: Speeds are designated in the product name numerically, e.g. NF-S12B redux-700 is 700rpm, NF-S12B redux-1200 is 1200rpm.
   • chromax: There is only one speed per fan version in the chromax line.
   • industrialPPC: Speeds are designated in the product name numerically, e.g. NF-F12 industrialPPC-2000 is 2000rpm, NF-F12 industrialPPC-3000 is 3000rpm.
6. Accessories: Redux and industrialPPC line fans come with mounting screws only whereas the standard-line fans come with a rich bundle of accessories (different cables, adaptors, anti-vibration mounts, etc., see individual specifications for details). The chromax line fans come with mounting screws and swappable anti-vibration pads in different colours.
7. Performance and application-type considerations for 120mm fans (airflow vs static pressure): In the 120mm range, Noctua offers the NF-A12x25 that provides superior performance in all applications and models such as the NF-F12 and NF-S12A or NF-P12 redux and NF-S12B redux that are focused solutions for either airflow or pressure-demanding applications. See this guide for further explanations. Note that there is no distinction between airflow and pressure-focused models in all other sizes. Except for the NF-F12, NF-P12 and NF-S12 lines, all other Noctua fans are designed to provide optimal results in both types of applications. In particular, Noctua’s A-series models are universal solutions that are excellent both as case fans and on coolers and radiators.
8. Popular choices and recommendations: Still undecided? Here’s a list of our most popular models of each size that have proven to work extremely well for the vast majority of users:
   • 140mm: NF-A14x25 G2 PWM
   • 120mm: NF-A12x25 PWM
   • 92mm: NF-A9 PWM
   • 80mm: NF-A8 PWM
   • 60mm: NF-A6x25 PWM
   • 40mm: NF-A4x10 FLX