The X-Keys keycaps are the best ones.
The RS ones are smaller in all three dimensions, though - which may be desirable under some circumstances.
I expected the X-Keys keycaps to have tinted lenses. They don't - the lenses are perfectly clear. The colouring is thus pretty subtle if you have opaque labels.
These keycaps look like they would work well with backlighting or keyboard LEDs.
This siteFrom here you can go back to My keyboard page.
KeycapsRS Components - UK