NFL players wear Guardian Caps to reduce head trauma during training camp
Guardian Caps, a soft-shell helmet cover, among CFL's new player-safety initiatives
NFL says positions wearing Guardian Caps saw 52% decrease in concussions - NBC Sports
NFL's use of Guardian padded helmet caps in camp draws support and skepticism - The Athletic
What are Guardian Caps and how are they helping football teams?
NFL training camps: Guardian Cap players are wearing over helmets, why
EXPLAINER: NFL using helmet caps for player safety, research
Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post
Guardian Protective Helmet Cover