D1 to BRFN-30 refill converter

I am very new to 3D designs, but I have test print this, and everything seems to fit just fine. 
I am using 0.4 nozzle Bambu Lab X1 Carbon with Bambu PLA filament. I use 0.16mm layer height to add a bit of precision, while the rest of the setting are default. The print will take about 30 minute to complete and the case is providing enough friction to hold the refill well while still remain easy to remove.  

Feel free to improve it if you have better ideas.

Cheers~