I'm looking at the hiwin hgr15, hgr20 and hgr25. Not a massive price difference for 500mm length.

I'm leaning toward the 20 but only because 15 seems small and 25 is possibly overkill.
I would have 2x rails on x-axis. I have never touched one of these so I'm guessing.

Not gonna jump in and buy straight away, just need to decide so I can mock up with correct dimensions.

Any recommendations would be warmly welcomed. Thanks.