The stock heatsinks that AMD includes with most of its Ryzen processors are quite capable but also relatively tall. The fastest Ryzens don't even include coolers. If you're building a Ryzen ITX machine and can't decide what to slap on your socket to keep things chilled, Noctua can hook you up. The company just announced the NH-L12S and NH-L9a-AM4, both updated versions of existing designs.
First, let's look at the NH-L12S. The previous NH-L12 came with two fans and had a slightly different shape. That cooler was versatile, but its installation could be complex. The new NH-L12S comes with a single slim-line 120-mm fan that makes it shorter than the previous model, even with the fan installed on top. Putting the fan there gives you extra room for tall memory modules, but if you're really strapped for space, you can install the fan underneath for a total height of just 2¾ inches (70 mm).
Like most of Noctua's current heatsinks, the NH-L12S comes with the company's new SecuFirm2 socket mounting system. That means it's compatible with pretty much every socket under the sun, including Intel's latest LGA 2066 and of course, AMD's Socket AM4. Given that the slim 15-mm NF-A12x15 fan is also Noctua-made, we don't imagine it will make a lot of noise, but the company includes a low-noise adapter in the box anyway.
Meanwhile, the NH-L9a-AM4 doesn't use the SecuFirm2 mounting system. This heatsink is designed specifically for the AM4 socket and is based on the original NH-L9a. This ultra-low-profile heatsink is just a hair under 1½ inches (37 mm) tall, including the fan. Even though this mini-cooler is ridiculously tiny, Noctua says it should be able to handle the heat output of the top-end 95W Ryzen CPUs, as long as they aren't overclocked.
Noctua's "no-overclocking" caveat extends to both of these coolers, although we suspect the NH-L12S could dissipate quite a bit of heat with a beefier fan on it. The company says both of these coolers are already shipping, and that it expects the NH-L12S to go for $50, while the NH-L9a-AM4 should be $40.