EXPLAINER: NFL using helmet caps for player safety, research
Guardian' helmet caps help protect Herd linemen, Marshall Sports
The story behind those soft-shell puffy Guardian Caps players have been wearing
If a player wanted to wear a Guardian Cap during a game, the league would prohibit it - NBC Sports
Guardian Caps leave some NFL players and coaches with concerns: 'You feel like a bobblehead'
Guardian Caps (@guardian_caps) • Instagram photos and videos
Packers share thoughts on wearing Guardian Caps at camp
What Pros Wear: Guardian Caps What are Those Helmet Covers Being Worn in Practice? - What Pros Wear