Every mechanical keyboard ships with keycaps made of one of two plastics. The difference shows up after about a year, which is exactly when you have stopped thinking about it.
ABS goes shiny
ABS is softer and cheaper to mould, which is why most keyboards come with it. Skin oil and friction polish it. After a year of daily use the keys you hit most - W, A, S, D, E, the space bar - develop a gloss the others do not have. The board starts to look worn in patches rather than evenly.
ABS is not bad plastic. It takes sharper legends and it can be made thick. It just ages visibly.
PBT keeps its texture
PBT is harder and more heat resistant. It holds its slightly grainy surface for years instead of polishing up, and it sounds a little deeper because the plastic is denser.
The catch is that PBT shrinks as it cools in the mould, so cheap PBT sets can sit unevenly on the switches. Worth knowing before assuming PBT is automatically better.
The part nobody mentions: how the legends are printed
The plastic matters less than how the letters got onto it.
- Pad printed - ink sitting on top. It wears off. Avoid.
- Dye sublimation - the dye is driven into the plastic. It cannot wear off, because there is no layer to wear.
- Double shot - the legend is a second piece of plastic moulded through the cap. Also permanent.
A dye-sublimated ABS cap will outlast a pad-printed PBT one. Check the printing before you check the plastic.
When none of this matters
If you replace your keyboard every couple of years, or you use it a few hours a week, buy whichever looks right to you. The ageing difference needs both time and hours to appear.
What we stock
The XDA Marshmallow set is PBT with dye-sublimated legends in XDA profile - every row the same height with a flat top, so there is no row order to get wrong when you fit it.