If you're the sort of person who regularly packs up their rig for conventions or LAN parties, you know how much of a pain it is getting everything bagged, all the cords wrangled, and the entire mess compressed in a way that it's (relatively) portable. For anyone who regularly moves their machine, or for people who want the best gaming keyboard experience when deploying their laptop in coffee shops or at the library, the SK621 may feel (at least in some ways) like manna from the heavens.
The SK621 is Cooler Master's smallest, low-profile board, not only sans tenkeys but also with the navigation keys compacted into the right side of the board (delete and the arrows remains discrete while the rest have been added as functions to other native keys). The tiny form factor adds to the aesthetic appeal of this little deck, not much larger than a tablet, and it features a gorgeous burnished aluminum top plate and per key RGB lighting. It's the perfect fusion of a chiclet keyboard and a proper mechanical deck, at least in terms of form factor.
Unfortunately, the experience of typing on it is much less satisfying. Because the deck is so compressed and the keys are flat and positioned so close to each other (a mere 2mm separates the keycaps, as opposed to the 5mm - 7mm on most full boards), I found myself frequently mashing two keys at once. There's also something mushy about typing on the SK621, likely a combination of the Cherry Red switches and their low profile configuration, but the force required to actuate the keys is far too high for a chiclet-style driver. It's an odd thing to say about a keyboard, but handling and moving it was far more satisfying than typing on it.
Even with those caveats, however, it still provides a better typing experience than virtually any laptop keyboard, and is perfectly suitable for gaming as long as you're not in a hyper-demanding eSports environment. The 600 series also comes in two larger varieties, all of them marked by these distinctive low profile keys—the tenkeyless SK630 and the full-sized SK650. Of the lot, the SK621 is my favorite, sheerly by dint of its chibi chassis, but if you prefer your low profile switches in a fuller body, Cooler Master has you covered.