936 mm for the X axis? Leads me to believe that you are looking at a medium size router, say, 2 foot by 3 foot or so.
That looks pretty long for an 8mm dia screw. Might be prone to "whipping" at higher rates off feed.
I would think that they might be ok units on a little machine like the Taig or Sherline metal working machines.
I am biased to some degree but I like and am using, these:
http://www.danaherlinear.com/section...IT=Descrip&GI=
Simple, rugged, and resonably resistant to dirty, dusty environments, yet not real pricey (pricey is, of course , relative).