T-ring cover for Canon DSLR

The T-ring for my Canon DSLR is connected directly to a coma corrector for astrophotography, but I was missing a way to protect the t-ring side of the filter when not connected to the camera. 

So designed this cover that go over it, and turns clockwise until it locks to the t-ring, so it does not fall off. 

Printed at 0.15mm PLA on Prusa Mk3S+. 15% infill.