this place has em listed for $1330 USD but i think they are in japan so no idea how much shipping will be:

http://www.nengun.com/tein/mono-flex

 

Tien USA lists the Flex Monotube as 14kg front 12 kg rear. http://www.tein.com/mfpdamp.html

These sound like great street/track rates. Maybe a little on the stiff side.

If these are the rates then I need to be saving my pennies.

Here is a link to the miata forums discussion of a Tien Flex shock dyno. I know, I know...different car different suspension...never the less I am willing to bet that the FD Monotube is going to have very similar characteristics. Food for thought.

http://forum.miata.net/vb/showthread.php?t=166909