Helmet sizes for larger heads

[zemzero]

 I have an ATA helmet and an AM 2.0. The ATA is really tight, I can barely put it on or take it off. The AM 2.0 is better, I have some fans, batteries and an amp in it and it is still more roomy than the empty ATA.

 

 I'm looking to start a sandtrooper and as I already completed an AM 2.0 kit, I would like to see how other kits differ.

 

 Between the armor I'm looking at, how does the RT and TM helmet compare to the AM 2.0 helmet?

[gmrhodes13[Staff]]

AM is the biggest out there, I believe TM is around the same as ATA, RT a little larger.