NFL players wear Guardian Caps to reduce head trauma during training camp
NFL mandates use of Guardian Caps for training camp in 2022 - Cincy Jungle
DL, MSM NEWS 2004-2008 WTH Reversal in Middle by vanderKOK (Also For Sale), PDF
Guardian Cap debuts during minicamps in effort to reduce avoidable head contact
NFL exec suggests Guardian Caps worn to protect players during practices could one day debut in games
Could Guardian Caps be used during NFL games for player safety?, Pro Football Talk
Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
Puffy Guardian Caps Could Reduce NFL Player Concussions HowStuffWorks
Unpopular guardian caps could provide false sense of security
NFL rejects PU safety caps for regulation play, allows 'opt-in' for practice
Could Guardian Caps be used during NFL games for player safety?, Pro Football Talk
Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
What Pros Wear: Guardian Caps What are Those Helmet Covers Being Worn in Practice? - What Pros Wear