Roller Blind outside Cover

One of the outer cases of my Roller Blinds deteriorated to the point where the chain would either get jammed or derail and I couldn't open or close my blinds. Upon inspection, the interior mechanism was still in good working order and didn't need to be replaced.
There is a complete replacement kit available at Spotlight but none were in stock anywhere so I designed my own part.

I'm new to 3D printing and CAD design and this is my first useful design to solve my real-world problem.

Printed in PLA with 100% infill. Works fine on the blind that I had to fix however I've only just done the repair. Time will tell how long it lasts however that particular blind doesn't get much use anyway so it should last me quite a while in my circumstances.

The aluminum tube is 30mm in diameter.