Hello
I received my teck today, and i was curious about this as well since i want to change keycaps for a custom layout.
While the surface is slightly different on the TECK caps, they have the same heights/profile than the caps of my Filco.
Some pictures: (blanks are from TECK, marked are from Flico)
I'd say it's ok to order caps from any filco-compliant manufacturer like WASD.
Regards