This is a cover or a grip for a M8 screw nut. Because of it there is not wrench needed while trying to pull tight a screw nut on a screw which will safe you a lot of time searching for your tools.
You need to pause your print at 7.75mm to place the screw nut inside of your print.
If you want to have another size, just write me a comment or remix it yourself.
Printed with yellow PLA