Smith] NFL says positions wearing Guardian Caps saw 52% decrease in concussions : r/nfl
Why are NFL players wearing padding on helmets at training camp?
What are Guardian Caps? NFL's latest padded helmets for added safety
Guardian Caps leave some NFL players and coaches with concerns: 'You feel like a bobblehead'
Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post
NFL expands rule against misuse of helmet; Guardian Caps required in regular season, postseason
Bombers set to don Guardian Caps” on helmets at training camp
EXPLAINER: NFL using helmet caps for player safety, research
NFL CMO Dr. Allen Sills explains importance of mandated guardian caps during training camp
NFL hopes to reduce head injuries with helmet experiment
So what exactly is that black padding on the Syracuse football helmets seen during practice?
September 2013 – The Concussion Blog