Original Message

are you buying a new HGU56? And if so, from a authorized distributor? If that's the case, the distributor will help you in sizing. Gibson and Barnes use to have a sizing guideline on their website. Also, check the Gentex site for help. They have or had maintenance manuals for the SPH series and HGU series that you can download, each with sizing guidelines. Don't buy a used military helmet unless you have the ability to change out the electronics. They don't work well in civil aircraft without modifications.