What are Glacier Peak players wearing on their helmets?
Large Bubble Helmets Are Guardian Caps, NFL's New Safety Measure
Guardian cap' to prevent head injuries mandated for practices, CFL says
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
Puffy Guardian Caps Could Reduce NFL Player Concussions
NFL Makes Ruling On Players Wearing Guardian Cap During Game - The Spun: What's Trending In The Sports World Today
NFL says Guardian Caps reduced concussions by more than 50%
Guardian Caps, a soft-shell helmet cover, among CFL's new player-safety initiatives
NFL players don Guardian Caps, designed to protect from concussion
NFL training camp 2022: Why are players wearing Guardian Caps?
Guardian Cap Debuts at Training Camps League-wide
What's with padded helmet caps teams are wearing
Why are NFL players wearing padding on helmets at training camp?