Fairly simple print, has been tested several times, 1:1 Scale.
Assembly instructions can be found here:
This helmet was originally for free, yes. Sadly some individuals see fit to download and then on-sell the files and profit off others hard work, so for this one it has been changed to a paid download.
Just to give you an idea, they were charging $130 Euros for these files behind my back - I am charging $13, less than 1/10th.
Print at 0.2 or lower for the best results, some parts may require supports.