Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post
Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
NFL expands rule against misuse of helmet; Guardian Caps required in regular season, postseason
NFL offseason priorities for 2023: Possible rules changes, safety reforms - ESPN
Guardian Caps: Why some NFL players are wearing them in training camps
NFL players wear Guardian Caps to reduce head trauma during training camp
What's With Those Padded Caps NFL Players Are Wearing In Training Camp?
Guardian Caps leave some NFL players and coaches with concerns: 'You feel like a bobblehead'
NFL starting on a long, strange trip
Guardian Caps leave some NFL players and coaches with concerns: 'You feel like a bobblehead'