Guardian Caps: NFL requires use of helmet cover at training camps to reduce head injuries : r/nfl
NFL players don Guardian Caps, designed to protect from concussion
NFL hopes to reduce head injuries with helmet experiment
Scene from Shrine Bowl: Why do players cover their helmets in decals? It's what makes the Shrine Bowl the Shrine Bowl
What's with padded helmet caps teams are wearing
The story behind those soft-shell puffy Guardian Caps players have been wearing
What Pros Wear: Guardian Caps What are Those Helmet Covers Being Worn in Practice? - What Pros Wear
Safe to say nobody at Patriots camp is missing two-a-days - The Boston Globe
Why are NFL players wearing padding on helmets at training camp?
Why Chiefs players are wearing special foam caps over helmets
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
Why Alabama football players are wearing padded helmets in practice
Raiders, other NFL teams wear Guardian Caps for head safety, Raiders News
Playing with a pillow on your head': Buffalo Bills embrace new helmet covers