Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
What Pros Wear: Guardian Caps What are Those Helmet Covers Being Worn in Practice? - What Pros Wear
The story behind those soft-shell puffy Guardian Caps players have been wearing
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
Arizona Cardinals defensive end J.J. Watt not fan of the new league-mandated Guardian Caps on helmets
What are the padded helmets players are wearing at NFL training camps?
Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post
What in the world are those weird-looking helmets the Saints are wearing in camp?, Rod Walker
Raiders, other NFL teams wear Guardian Caps for head safety, Raiders News