Its a filament guide that is wide as has a large oval hole
It fit REALLY tight so depending on your printer you might want to increase scale by a % or 2
Mine is PLA 20% infil
I do not knwo if having a larger hole is better, but it works fine for me.
Original STL was from Ismael Feliciano, I took what he did as a stencil and made one the same basic shape only wider