<img src=
http://www.hornell.com/hsi/promot.jpg>
http://www.hornell.com/hsi/proupman.jpgmaybe these images will help you understand what the protop "rail" system does as compared to the universal slot adapter (rabbit ears). now as far as fitting other hard hats, im not sure if the strap is adjustable, but the speedglas hardhat has a small or non-existant brim to allow you to get a closer fit without having to reverse your hard hat and suspension.
04-0315-00 Speedglas ProTop strap ( for just the hardhat rail system )
04-0215-00 Speedglas ProTop hard hat with headgear