LV - Cat's eyes and NBC boot cut-off doesn't really serve much of a purpose except looking good. However, as with all ally kit it must have a pretext.
The NBC boot helps to stop the cover from slipping off, it also protects the cover it a little when you put your helmet down.
The Cat's eyes is good for writing your name on, plus blood type and "NO PEN" etc. It's also good when stumbling along in the pitch black as you can see the bloke in front.
Just make sure you get the photoluminescent ones rather than the retroreflective ones.