[crossup]

Im trying to decide what type of x/y rail to buy for a laser with a work space of 1000-1600mm by 600-800mm. My choice is between aluminum extrusions with round cross section rods in groves on the rail sides(hence the term "outer slider" and aluminum rails which have a linear guide on top which has a car that rides in the side grooves.
First picture is the outer slider, second the linear guide. Question is which is better for precision. I'm sure the steel out rail is more durable but not sure is its as precise

[awerby]

If that's a steel rail attached to the aluminum extrusion with the outer grooves in the sides that fit ball-bearing trucks that ride along it, then that would be more precise, as well as more durable.

[crossup125]

Sorry for not being clearer but I'm having some sort of glitch here and cant edit my post. This post has an edit button, my first post does not.

The left hand photo is the Linear guide which I believe has ball bearing cars on an alloy track(very similar to sailboat hardware I'm familar with)on top of the structural rail and the right hand picture shows the "outer slider" where the track is round rod on the side of the structural rail with grooved rollers as the moving part. So I guess neither is what you were describing

[awerby]

The first one was what I was describing. On my screen your photos are on top of each other, not side-by-side. The one to use is in the top photo; that type of rail is more expensive, but more precise.