Closer Examination

As we saw before, the Cooler Master SK621 comes in a nice drawstring carrying pouch, which makes for a relatively premium unboxing experience. This also makes sense with the more portable nature of the SK621, although there is not a lot of room inside if you want to include the detachable keyboard cable as well. The keyboard itself is extremely light at under 0.5 kg, which also adds to the portability factor in addition to the whole wireless connectivity option. Indeed, there are minimal bezels all over to make for a keyboard that is on par with some 45% form factor keyboards. It looks just as great as the SK630 we saw before, with the brushed aluminium frame and a chrome ring for some accentuation on the sides (remember to peel off the protective plastic) adding some flair to this extremely clean design. There is no branding anywhere except for the subtle new Cooler Master logo on the Fn keycap in the bottom row.

There is no numpad here, and indeed far fewer keys than even on the TKL form factor SK630. The SK621 is a 60% form factor keyboard, which is not really a standard in that Cooler Master was able to choose which keys to retain and omit. In general, the Fn key row is lost with all 60% keyboards, as is the case here, and we have some of the more used keys given discrete buttons; Del, for example. Keycap legends are also arranged such that secondary legends are either along the primary ones (if generally associated with the key) or underneath (if layered as a result of the smaller footprint available), and all single legends on keycaps are at the top center, which hints at where the backlighting on the keyboard will be biased towards. Overall, this is a keyboard you can take around and use in any environment—home or work—and the carrying pouch combined with the increased portability adds to this use case.


Flipping the keyboard around, we see the usual certification sticker, but it is situated closer to the bottom this time around. There is instead a full-size Cooler Master logo where it would usually be, just in case you forgot who makes and sells this keyboard. Four rubber pads on the corners also keep the keyboard from sliding around on the desk, and this is it as far as any further available elevation goes. Cooler Master wants to have as low a profile with this keyboard as possible, within reason of course, which accounts for the ~30 mm overall height.


The keyboard has an inset USB Type-C port in the center of the side facing away from the user and typically closest to the PC/USB hub. The provided cable fits in snugly here and connects to an available USB Type-A port on the other end. USB 2.0 will suffice for power and data in wired mode, although most motherboards these days come with an abundance of USB 3.1 Gen 1 (USB 3.0) ports, which is recommended for the various RGB LEDs onboard.


The keycaps are low in profile with a predominantly flat top surface and cut sides to where they have more in common with chiclet/scissor switch keycaps than a typical mechanical switch keycap. There is an overall slant, which helps given the lack of keyboard feet, but otherwise, it is not easy to distinguish between the various rows when touch typing. They adopt a floating design given the lack of a top case panel, and the included keycap puller is really overkill in this case but appreciated for when you have to remove certain specific keycaps amidst others for disassembly, as seen on the next page. Build quality is so-so with thin ABS and laser-etched legends making them prone to showing signs of wear and tear sooner rather than later. Primary and secondary legends are backlit, albeit to different extents depending on the placement of the LED underneath. Note also the toggle switch on the side that turns on/off Bluetooth on the SK621.


The Cooler Master SK621 only comes in one switch option at this time, as with the rest of their SK keyboard lineup, and that happens to be the relatively new Cherry MX Low Profile RGB Red. We saw Cherry unveil these at CES 2018, and I can still count on the fingers of one hand the number of keyboards with this switch to date. It is Cherry's take on updating their low-profile mechanical switches, which used to be the role of the Cherry ML switch, with all new tooling and design for improved backlighting while still attempting to retain the typing feel of the larger MX Red switch. The larger keycaps, and this is applicable mostly to the space bar, use a thin wire stabilizer as seen above. One thing I noted here is that the squared keycaps have enough give in them to where they can be angled slightly to the left or right, which makes for a less appealing look if you care to look deeper at the keyboard.