the US military is in process of replacing the pasgt with the Advanced Combat Helmet (ACH)....they are starting to use MICH helmets but the marine corps still uses the pasgt style helmet...all helmets are being replaced with foam padding inside the helmet for added protection...
the mich is smaller and protects less area but in my opinion... the mich gives u a better field of view than the old pasgt...the downfall with the mich is that a real one can cost anywhere from $200 to $600.....i've seen pasgt go for as low as $50....if u really wanted to...u can change the suspension system in ur pasgt
here is wat the marine corps and other forces use to upgrade their helmets
http://www.oregonaero.com/p81_2001.htmlfeel free to ask anymore questions...i hope this info was useful