What's in a few millimetres? A lot, apparently, according to Noctua. The iconic cooler/fan manufacturer has announced a minor adjustment to its fan designs: adding a small offset on the corners. This 5mm riser means that the fans will need to be a tad smaller to fit in the same spaces, but it makes an important difference. By moving the fan away from any grills or dust filters, it reduces air turbulence, improving fan efficiency for moving air, and reducing noise levels in turn.
When it comes to cooling fans, Corsair and its ilk might think that the main interest is RGB lighting, but in actuality, the main benefit of them is to keep your system cool. You don't want them to be too loud, though, even if you are gaming in headphones, and Noctua has regularly set the pace when it comes to that mix of cooling and quietness. These spacers may only improve that a little, but every little helps when it comes to making a quiet PC.
Noctua has said it will sell the offset spacers separately, as well as including them on upcoming fan designs, so you can add them to your existing cooling setups if you wish, or upgrade to the new fans in one move. They're not cheap though, with each kit of the funky-named NA-IS1 offset spacers setting you back around $15 USD for a set of two.
Still. Could be worth it.
