This is a simple case for a set of ER11 collets used on small CNC machines.
I recently built my own small CNC machine from salvaged and 3D printed parts. The chuck I used on my spindle motor was an ER11 chuck. I ended up buying a set of 7 ER11 collets to use with the machine, but they didn't come with a case of any kind. I did a search on thingiverse, but could not find a case to hold them.
I designed this basic case using OpenSCAD with 8 collet spaces and a lid. It is nothing fancy, no hinge, no latch to keep the case closed, but all I needed was a basic case.
Hope others may find this useful.