Compatible with all Noctua 12V fan. 4-pin connectors support both 3-pin and 4-pin PWM fans. Low-Noise Adaptors for reducing the running speed and noise emission of PC fans.
These adapters do the job they're suppose to. Unless your fan are running full speed, you might want to reconsider using these, as they cut the speed down to about half of full. For the price, you can't go wrong buying these.
The ONLY reason I give them a 4 star rating, is that they DID cut the speed a little more than I wanted, but the fans still and there was no manual or specs that could have given a clue as to how they would work with different fans with different loads and speeds.