PLA Slider for 1515 Extrusion

I plan to use this on my Mini Kossel delta printer instead of the existing shower roller carriages. They fit perfectly and have zero play in them. They do not wrap all the way around the 15mm extrusion because I am using the back side of the aluminum extrusion to hide the end stop wiring and I have printed wire covers.

youtube video to show how they should work:

https://www.youtube.com/watch?v=hfuVoxgvb8U

Update: I redesigned this and made it a bit better in the anti-twist department