Shell for Fabric Pen Refills

This is a simple pen shell for “magic” disappearing ink cartridges used for fabric marking. These cartridges (used for sewing but also for my kids' magic ink workbooks) did not fit in any pens I had, so I made a custom shell. The refill cartridge I designed it for measures approximately:128 mm tip to end15 mm tip to plastic collar1 mm thick plastic collar 3.2 mm diameter plastic shaft just below tip5.5 mm diameter plastic collar4 mm diameter main shaft