What Pros Wear: Guardian Caps What are Those Helmet Covers Being Worn in Practice? - What Pros Wear
Guardian Caps Guardian Sports
Guardian Cap Use a Concern for Watt, Saleh Early in Training Camp - Sports Illustrated
Guardian Cap Debuts at Training Camps League-wide
Guardian Protective Helmet Cover - XT Model
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
The story behind those soft-shell puffy Guardian Caps players have been wearing
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
Raiders, other NFL teams wear Guardian Caps for head safety, Raiders News
EXPLAINER: NFL using helmet caps for player safety, research