The world of custom mechanical keyboards is incredibly varied with boards of all shapes and sizes. You can get small, lightweight boards, but there's a trend toward large, monolithic cases. It's not necessarily a contest to make the heaviest keyboard possible, but that's often the consequence of designing something interesting. Australian designer Rama is no stranger to making hefty keyboards. His latest project is the Koyu, a big, imposing 65% board that'll put a similarly big dent in your bank account.
Since this is a 65% board, there are arrows and a number row, but no number pad. The layout is also a bit more compressed than a standard tenkeyless board. It also uses an HHKB-style backspace directly above Enter, which you may not be accustomed to seeing. It has a single USB Type-C port, and the entire chassis is inclined at 8-degrees for improved ergonomics.
Inside, the Koyu runs on a hot-swappable PCB running the QMK firmware. This is an increasingly popular option as it's both powerful and open source. Since it's fully programmable, you can change the function of any key on the board and configure the function layers to do whatever you want. The hot swap sockets mean no soldering, and you'll be able to change the switches whenever you want. In addition, each switch includes integrated RGB LED lighting in the board (also fully customizable via firmware). As long as your switches have transparent housings or a light pipe, you'll be able to see the light shine through.
The Koyu uses an integrated aluminum plate design. That means the plate is part of the solid aluminum top case and it's 4.5mm thick (several times thicker than most keyboards). This makes the design a bit less flexible, but integrated plates also tend to make a board feel sturdier. That's definitely in the Koyu's wheelhouse. The base model keyboard weighs 1.7 kilograms (3.7 pounds), but that's just because it's a block of aluminum. If you want it to be heavier, there's an optional internal brass weight that adds another 0.8 kilograms of mass.
When a keyboard is heavy, that's probably a sign that it's well-built. A custom board that pushes the weight to a few pounds also stays put on your desk and doesn't slide around. You can take the Koyu even further with the special edition "Tank" model. This version has the same design and features, but it's milled from a solid block of hand-polished, PVD-coated brass instead of aluminum. Brass is much more dense than aluminum, so the Tank weighs in at an impressive 4.4 kilograms (9.7 pounds). You can even add that optional brass weight for a total mass of 5.2 kilograms (11.5 pounds). That's by far the heaviest keyboard of which I'm aware. There's also a middle ground option with the Tank's brass top and an aluminum bottom (3.4 kilograms).
The base model Koyu clocks in at $360, which is competitive for a high-end 65% kit. I've seen similar kits go for far more. The Tank edition is much more expensive at $1,000, and the Tank Lite is $800. These special edition boards will obviously appeal only to the most committed keyboard aficionados. Pre-orders for the Koyu are live until the end of November, and they'll ship in a few months. This kit doesn't include switches or keycaps.