I purchased the redi rail on ebay, 36" for $87. The redi rail cars came from 2 smple requests, one that I made about a year ago and one that another coworker made independently. when I saw he had it, I asked if he needed it. He didn't, and gave it to me. Regarding the Uniglide, the specs are rock solid. There does seem to be a slight bit of runout in it, but I assume it is the same for all rail/solid bearings. It is solid with just enough screw holes to easily fit the bill. I'd certainly use it again for the z axis. The nice part is that it is really 2 rails in one piece built 3" apart from eachother and a 4" long pair of bearings in one solid car. This design automatically aligns the left rail to the right rail since it comes as one piece.

regarding the redi-rail, i cannot feel or measure any runout at all in this system.

samples took about 3 weeks to arrive as I recall.