I had a spare PureBase 500 laying around that I wanted to use for my NAS/Homeserver becasue it has sound dampening and quite large fans that I can run pretty slow but originally this case can only hold 2x 3,5" drives.
This adapter has holes for four M3 threaded inserts and screws in the holes for the 120mm front fans. This way you can still mount some 140mm fans for cooling.
You need to print it twice: The original STL is the left holder (when you look at the case from the front) and the right one has to be mirrored. I create a small notch on one of the rails to help with orientation: The notch has to be facing inwards on both parts.
The author marked this model as their own original creation.