I got hold of some of these keys recently.
First impressions - built to really last - lots of material.
Don't take Rit dye (or didn't when I asked them to).
Slightly bigger (1mm longer - north to south on the board - very close east to west and about 2mm higher) than filco switches.
Shame they don't come in a variety of colours and profiles.
Oh, if you are going to try the Rit dye, I know they can stand 80 degrees Celsius in a preheated jug until the water cools down - no sign of distortion.
Available from
http://uk.rs-online.com/web/ part number 333-861
quick edit - the black key is the escape key from my filco...