9mm Belts vs Screw Drive

I was looking around the forum to see if anyone did the linear bearing upgrade on the Y and X there was one who started doing it and I have tried contacting him, but got no reply yet, I am still looking around at what is available and found these, I am in the UK, I was wondering if the rails need 2 sliders or just 1, the rails would fit where the belts were, and could be fixed with T-nuts, as I have a screw-drive now instead of belts
https://uk.rs-online.com/web/p/products/4885091/
this is a link to the other thread
Replacing V Wheels with Linear Guide bearings