This is a Magazine sleeve adapter for P365 FUSE 21rd mags. It is designed for the standard base plate that comes with P365 9MM 21RD MAGAZINE. It closes the gaps and improves grip when used with Sig Sauer P365X/XL grip frame.
It should not interfere with the insertion and locking of the magazine, and should release normally when magazine release is pressed. Make sure the sleeve is firmly and evenly positioned as low on the magazine as possible. If you feel additional tension when trying to insert the magazine or if it fails to lock, sand down the lips of the magazine sleeve to fit.
Print upside down with supports enabled on the overhang:
I recommend printing with fuzzy skin. New PrusaSlicer 2.9 fuzzy skin painting tool works great for this. Make sure to apply fuzzy skin only on the exposed parts and not to add fuzz to any internal surfaces or parts that interface with grip frame like this:
I printed in Polycarbonate, any strong heat resistant filament should work. I would not recommend PLA if you live in a warm climate as it has potential to deform if left in hot car.
The author remixed this model.
Made several sub millimeter changes to dimensions for better fit inside magazine well. Removed front lip because IMO was thin and prone to breaking. Extended rear grip section for longer fuse 21 round magazine.