This is the Clone Trooper helmet from Star Wars - The Clone Wars
You will find a 3D model of the helmet (without the lenses, so that you can add transparent ones). It is 1:1 scale, but you will have to adjust the size yourself to make sure it fits your head's size :) You also have to split the model accordingly to your printer's printing volume :)
These files are for a personal use only
Happy Printing :D