I needed a cap for a square metal pipe to keep things out of it and protect me from it's sharp edges. The square pipe has an outside (OD) of 40mm and the cap is just a press-fit.

Here is my 3D design. My design may match your needs, too.

My print is made in 1.75mm eSUN PLA+ filament, with 0.2mm layer height and 15% infill on a Bambu X1 Carbon printer. Print supports are not required.

I hope that you can find this print useful, too.

Remember to leave me some feedback or even a tip to keep me enthused to make more of these drawings.