It is definitely a One-size.  got to complete kid's costume, was a bit large.  Spray painted the helmet gold , and while the look was great, the mateials (vinyl and cloth) took a while to cure, and then still had a bit of a tacky  feel to them.  Overall, it did the job.  It's still used by the kids for play.  Just keep in mind that the helmet IS floppy due to soft materials used.