I will give props to Cooler Master for holding true to their promise from last year that they would bring out low-profile mechanical keyboards in various form factors within a spate of months, beginning with the SK650/SK630 in January this year and now the SK621 for not only a third different form factor, but the first of their SK keyboard lineup to offer the hybrid Bluetooth or USB connectivity options. The SK621 is the best fit for this, too, with its extreme portability very handy for those in the office with a cluttered desk, or just gaming at home where you would like the mouse to be closer to the keyboard. Most people do not use more than a 60% keyboard-worth of keys, and a dedicated numpad comes in handy for when it is a must. For those wondering, the SK621 makes for an excellent macro pad—be it for applications such as from the Adobe Creative Suite or just RTS games in general. This is also Cooler Master making sure they have something for everyone, which is not trivial for a mainstream company to commit to. I appreciate them trying out new things for niche audiences, even if things may not have worked out in the past with such ventures.

I am indifferent on pricing, if only because there are not many others with low profile mechanical switches in the TKL form factor. Many are using Kailh switches, but their feature set is so different they might as well be something else, especially given the small intersection of customers who look at those and the options from CORSAIR and Cooler Master using Cherry switches. I also do not know of any other keyboard in this form factor that employs these switches, and finding one with low-profile switches is extremely hard as well given the limited market. Cooler Master is aiming for a different market here compared to their other keyboards, such as the MK series that throws the kitchen sink on a keyboard and then some, and this market likely will have made up their mind about the SK621 irrespective of the price.

Unfortunately, there are more issues with the SK621 than I would like, and no more egregious than Cooler Master recycling the older version of Portal with limited functionality on key mapping and a worse user interface than the one they already have worked on and put out for the MK850 keyboard from earlier this year. There is no excuse for this, especially when having an open firmware for full reprogrammability is an extremely important metric for customers looking at 60% or similar form factor keyboards. The hit-or-miss Bluetooth connectivity is another issue of note even if it may be a one-off with my situation, and I can only wonder if the adoption of a newer Bluetooth standard than 4.0 might have helped mitigate some of this. As it stands, I am unable to recommend the SK621 to everyone. I can only encourage you to look at options before committing to it should you be in the market for a portable small form factor mechanical keyboard.