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Cooler Master SK621 Low Profile Mechanical Keyboard Review

Paul Eno Posted:
Hardware Reviews 0

Being on the move can almost be considered a necessity in today’s societies. Whether going to work, school, running errands, attending gaming events, or just picking up food, there are a plethora of things to do and that require attention that force us to keep moving. Part of that means dealing with new and different situations on a regular basis, and for some of us, new and different hardware. Maybe not so much anymore. Enter the Cooler Master SK 621, the highly functional, quality, and portable solution for those of us sick of using other people’s wonky keyboards and settings. Here is our review of this streamlined and versatile compact keyboard.


  • Keyboard Switch Type: Cherry MX RGB Low Profile Switch
  • Material: Aluminum, Plastic
  • Color: Gunmetal
  • Keyboard Polling Rate: 1000Hz
  • Keyboard Response Rate: 1ms /1000Hz
  • Keyboard MCU: 32-bit ARM Cortex M3
  • Onboard Memory: 512KB
  • On-The-Fly System: Multimedia, Macro Recording and Lighting Control
  • Multimedia Keys: Through Function Key (FN)
  • Software: Via Cooler Master Portal
  • Wireless Connectivity: Bluetooth 4.0
  • Cable Length: 1.8m, Braided & Removable
  • Keyboard Dimensions: 293(L) x 103(W) x 29.2(H) mm
  • Weight: 424g / 0.934lbs (without cable)
  • Warranty: 2 years

In the Box

  • SK621
  • Travel Bag
  • 1.8 Meter USB Type-C to 2.0 USB Type A Detachable & Braided Cable
  • On-The-Fly Multimedia, Macro Recording, and Lighting Control Manual
  • Bluetooth 4.0 Wireless Connectivity Manual

The first thing you’ll notice about the Cooler Master SK621 is that it is teeny. Cooler Master describes it as compact and they aren’t kidding. This keyboard is a minimalist’s dream and at 60% of the size of a traditional keyboard, it takes up a comparatively small amount of desk space, which I love. This keyboard is incredibly streamlined, and I wish I could say that it streamlined or decluttered my desk, but a minimalist I am not. So, it just provided more space for random stuff. But it’s important stuff. At least that’s what I tell my wife when she tells me I should clean it off.

Like many of the compact keyboards, the SK621 does away with the ten-key input, as well as the input keys in between the ten-key and the main alpha-numeric interface. But don’t freak out! All of the essential keys are still there, simply rearranged or added as an alternate function on another key. Honestly, the ten-key is just a repetition of keys already placed elsewhere on the keyboard anyway. Except for the Number Lock key, and what use was that, anyway?

The whole point of this design is the low profile with its compact size and suspended, slim keys, Bluetooth 4.0 for power efficiency, and the flashy LED RGBs… Okay, so maybe not that part. If you really are looking to maintain a low profile, the lighting can be turned off. Or simply switch profiles. The SK621 has a full range of lighting options as well as onboard memory for saving up to four profiles that you can switch between either on-the-fly or using the Cooler Master Portal software plugin.

The Cooler Master Portal software really is easy to use, intuitive, and easy to understand. All-in-all, the software is great, allowing users to set lighting preferences, create and set macros, define individual profiles, adjusting wireless LED and power settings, and remapping or disabling keys. In other words, it gives the user a lot of options with a simple interface.

Now, as cool as that is, almost all of that can be done using just the keyboard, except the key mapping and key disabling. Through various key combinations using the Function key (identified by the Cooler Master symbol outline), nearly every option you can find with the software can be selected or changed at your whim. This is important, as one of the biggest assets of this keyboard is its capacity for easy portability and its ability to function seamlessly wherever you take it. Which should be anywhere.

From cycling through quick-pick colors and modes with Function + Tab to changing the shaded and intensity of the colors by flipping through different levels of each of the RGBs using Function + Q (red), W (green), or E (blue). Other aspects that can be controlled from the keyboard itself include lighting modes and effects, both foreground and background, macro recording with a choice of different looping parameters, and switching through the four different profiles.

The size of the SK621 and its included carry bag makes it ideal for toting it to any location for convenient use. With Windows 10, it will simply plug-n-play using the onboard profile you choose. That means that specific macros, lighting effects, or key mappings that you have associated with your profiles will still be usable regardless of what computer you’re plugged into.

With the 4.0 Bluetooth compatibility, your hookup options multiply and even allow you to pair with your tablet. No more swiping or finger-picking long emails. With a quick flip of a switch located on the left side of the keyboard, you’ve activated the Bluetooth function. From there, you can either wait for the keyboard to cycle through the channels until it finds a compatible device on one of its three channels, or by simply pushing a combination of Function and either Z, X, or C to instruct the keyboard which channel to use. Once a channel has been designated to a device, future linkups are as simple as designating the corresponding channel. The SK621 has up to three Bluetooth channels that will allow you to pair it with three devices, and switching between them is a breeze.

Performance-wise, Cooler Master has packed in all the goods to ensure a quality experience. Low profile Cherry MX switches ensure a lessened distance and actuation point while still providing the durability, tactile feel, and precision we are accustomed to. A 1000Hz polling rate with a key response of 1ms/1000Hz provides a more than adequate response rate for daily use and casual gaming. The ability to create and assign your own macros more than makes up for the loss of excessive keys the fully customizable LED lighting system lets you show your true colors.

Final Thoughts

The Cooler Master SK621 is a streamlined, portable, and versatile tool. Slim and sleek with its low profile design, it is ideal for carrying with you and the ability to switch quickly between profiles without software assistance lets you have an ideal setup ready for whatever aspects of your life you need it for. The build is of quality that you can feel and see, and the design makes the most use of minimal space while the lighting options give it a substantial amount of flair. For myself, I’m quite pleased with the product's functionality, feel, and customizability. So much in such a small package.


  • Very portable
  • Takes up very little space
  • Full feature control without the need for software
  • Quality build and parts


  • Larger hands might find it awkward
  • Can’t use key codes to insert subscript and superscript symbols

The product discussed in this article was provided by the manufacturer for the purpose of review.


Paul Eno