Coolkiller ROCOCO Numpad vs MMD KM21 Ultra
Choose the Coolkiller ROCOCO for its gasket-mounted, foam-dampened build, or the MMD KM21 Ultra for its aluminum case, four clickable knobs, and QMK/VIA support.
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Which one should you get?
Get the
Coolkiller ROCOCO Numpad
Build quality in the bottom 45% of Numpad boards under $100.
- Gasket-mounted construction with poron foam and silicone damping.
- South-facing RGB LEDs.
- South-facing LEDs. Shine-through legends stay dark, and some sculpted keycaps can clip the LED.
Get the
MMD KM21 Ultra
Knob
Build quality in the top 15% of Numpad boards under $100.
- CNC-milled aluminum case with a plastic plate.
- Four clickable knobs, with QMK and VIA support for configuring controls.
- 980mAh battery for wireless operation.
Get the Coolkiller ROCOCO if its gasket mount and documented poron and silicone damping are your priorities, while accounting for the south-facing LED keycap caveat. Choose the MMD KM21 Ultra for its CNC-milled aluminum case, four clickable knobs, QMK/VIA controls, and listed 980mAh battery, features the ROCOCO does not offer.
The differences that matter
Skip the 40-row spec sheet. These are the specs that change how each board feels, sounds, and fits your desk.
Coolkiller ROCOCO Numpad
MMD KM21 Ultra
Case material
ABS
Aluminum
Mount style
Gasket Mount
Top Mount
Knob
No
Yes
QMK
No
Yes
The deep option when you want to remap every key
VIA
No
Yes
GUI remapping without compiling firmware
- Coolkiller ROCOCO Numpad
- MMD KM21 Ultra
- Performance
- 5666
- Build quality
- 6181
- Productivity
- 6089
- Customizability
- 6389
- Portability
- 8385
- Layout size: Numpad
- Connection: Bluetooth, 2.4 GHz, Wired
- Hot-swappable
- Sound dampening
What will you mostly use it for?
The KM21 Ultra is the more workflow-oriented choice across office, programming, and content creation, largely because of its four clickable knobs and QMK/VIA support. It also has the clearest travel advantage in the listed 980mAh battery, though weight and dimensions are not available for a direct portability comparison. For modding, the KM21 Ultra offers broader documented configuration, while the ROCOCO is distinct for its gasket mount and foam-and-silicone damping. Gaming also leans toward the KM21 Ultra for its configurable controls, but neither product's supplied details establish a specific gaming performance advantage.
Pick the MMD KM21 Ultra
- The KM21 Ultra supports QMK and VIA, with vendor-described key remapping and macros.
- Its four clickable knobs can be assigned controls through VIA, according to the vendor.
- The ROCOCO's south-facing LEDs may clip some sculpted keycaps.
Coolkiller ROCOCO Numpad vs MMD KM21 Ultra specs
Every tracked spec, side by side. Rows marked with a dot differ between the boards.
8 of 18 specs differ
Coolkiller ROCOCO Numpad
MMD KM21 Ultra
Hot-swappable
Mount style
Sound dampening
Layout size
Layout standard
Ergonomics
Knob
Display
Connection
Battery
USB-C
Case material
Plate material
Backlight
QMK
VIA
Mac & Windows
Released
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Coolkiller ROCOCO Numpad vs MMD KM21 Ultra: your questions
Choose the ROCOCO for its gasket mount and poron and silicone damping. Choose the KM21 Ultra for its aluminum case, four clickable knobs, and QMK/VIA support.
The KM21 Ultra has four clickable knobs, and its vendor description says they can be configured through VIA. The vendor also describes uses such as volume, zoom, and timeline scrubbing.
The ROCOCO metadata does not list QMK or VIA support. Its vendor description mentions compatible software for DIY settings, but does not identify that software as QMK or VIA.
The KM21 Ultra has a CNC-milled aluminum case and a plastic plate. Its vendor description also names PORON, IXPE, PET plate material, and bottom-foam padding as damping components.
The ROCOCO uses a gasket mount with silicone gaskets. Its vendor description also names a poron foam switch pad and silicone sound-absorbing pads.
Both models are listed as hot-swappable. The ROCOCO vendor description specifies support for 3-pin or 5-pin mechanical switches, while the KM21 Ultra listing describes MX-style hot-swap.
Its south-facing LEDs may leave shine-through legends dark. The compatibility note also warns that some sculpted keycaps can clip the LEDs.
Both are listed with Bluetooth and 2.4 GHz wireless, as well as wired connectivity. The KM21 Ultra vendor description identifies Bluetooth 5.0; the ROCOCO vendor description identifies Bluetooth 5.1.
The KM21 Ultra is listed with a 980mAh battery. The ROCOCO listing does not provide a battery capacity, so a direct capacity comparison is not available.
The KM21 Ultra has four clickable knobs, and its vendor describes them for controls including timeline scrubbing, zoom, and volume. It also supports QMK and VIA for configuring keys and knobs.
Both are numpads, but the KM21 Ultra adds four clickable knobs and QMK/VIA support for assigning additional controls. Its vendor specifically describes it for spreadsheet and number-entry workflows.
Both are listed with RGB lighting. The ROCOCO specifically has south-facing LEDs, which can affect shine-through legends and compatibility with some sculpted keycaps.
Not sold on either?
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