Noctua NF-A12x25r PWM, Round-Frame 120mm Fan, 4-Pin Case Fan/Cooler – Brown The NF-A12x25r is a round-frame version of Noctua’s award-winning flagship model 120mm NF-A12x25 fan. Its round shape makes it ideal for use on low-height dual-tower CPU coolers like the NH-D12L as well as other space-restricted applications that cannot accommodate square-frame 120mm fans. Just like the square NF-A12x25, the round NF-A12x25r uses a record-tight tip clearance of only 0.5mm, which is made possible by using the novel Sterrox liquid-crystal polymer (LCP) compound as well as a metal-reinforced motor hub and axis for ultimate precision. Sharing the same state-of-the-art impeller design with Flow Acceleration Channels, the NF-A12x25r achieves the same class-leading quiet cooling performance as its square-frame sibling. It also supports fully automatic speed control via PWM fan headers and comes with a Low-Noise Adaptor to reduce the maximum speed from 2000 to 1700rpm. Its superior efficiency, cutting-edge construction and pioneering materials make it an elite choice for all 120mm applications that require a round frame. Round frame design The NF-A12x25r is identical to the NF-A12x25 except for its round frame that allows it to be used in applications where a square-frame 120mm fan would not fit. For example, the NF-A12x25r is ideal for being sunk in between the dual towers of the low-height NH-D12L cooler without causing compatibility problems with tall motherboard heatsinks or shrouds. Sterrox liquid-crystal polymer compound The NF-A12x25’s impeller is made from Noctua’s novel Sterrox liquid-crystal polymer compound that features extreme tensile strength, an exceptionally low thermal expansion coefficient and damping characteristics: ideal for reducing resonance and vibration phenomena in advanced fan-blade designs. Ultra-tight tip clearance The NF-A12x25 has a record tight tip clearance (distance between the blade tips and the inside of the frame) of only 0.5mm. This highly ambitious design sets a new benchmark for 120mm fans and helps the NF-A12x25 to work more efficiently against back pressure, such as on heatsinks or radiators, by reducing leak flows through the gap between impeller and frame. Metal-reinforced motor hub The centrepiece of the NF-A12x25’s motor hub is made entirely from steel and the axle mount is reinforced with an additional brass structure. In combination, both measures ensure ultimate precision and increased stability in the critical hub area. Therefore, it is not suitable for applications that require the standard 105x105mm hole spacing of square-frame 120mm fans such as PC cases, water-cooling radiators or CPU coolers with fan clips for square-frame 120mm fans.