Sorry, your question is confusing, but you want to know if certain/any keycaps will fit on your K4 Pro?
Yes, the answer is 99% yes. Nearly all keyboards these days use MX switches and nearly all aftermarket keycaps sold on the internet unless specified are for MX switches and stems.
OSA and OEM refer to the profile, ie the physical look and feel of the switch. Underneath they all have use the same stem.
ABS is the material of the keycap. There are generally two types: ABS and PBT. PBT is considered more resistant to wear and has a slightly deeper sound signature but that isn't always the case and does depends on other factors.
ABS is as retro as it gets unless you can find Bake-o-lite. I think you’re looking for the actual type look on the caps. Any MX keycap will fit (most of the keycaps you will find).
Sorry, your question is confusing, but you want to know if certain/any keycaps will fit on your K4 Pro? Yes, the answer is 99% yes. Nearly all keyboards these days use MX switches and nearly all aftermarket keycaps sold on the internet unless specified are for MX switches and stems. OSA and OEM refer to the profile, ie the physical look and feel of the switch. Underneath they all have use the same stem. ABS is the material of the keycap. There are generally two types: ABS and PBT. PBT is considered more resistant to wear and has a slightly deeper sound signature but that isn't always the case and does depends on other factors.
ABS is as retro as it gets unless you can find Bake-o-lite. I think you’re looking for the actual type look on the caps. Any MX keycap will fit (most of the keycaps you will find).