Round rails & bearing fit?

[Peter.]

Quick question here. I have the two used rails shown in the picture along with the four bearing blocks. No use for them so I thought I'd offer the pair for sale, but I noticed that the linear bearings have significant movement axially on their own. What i mean is, if I grab a single block I can rock it quite noticably length-wise ont he rail. If however I put a pair together they become nice and firm, there's no radial play that I can detect by hand. Is this normal or does it indicate significant wear?

[Jonathan]

Not sure about the bearings. There certainly shouldn't be radial play.
More interestingly, what motor is that as it seems to have an encoder?

[Peter.]

It's a 3-phase stepper. It has no encoder, though it has the facility for one.