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
NFL mandates use of Guardian Caps for training camp in 2022 - Cincy Jungle
Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
Rising concussion awareness leads one high school to invest in high-tech football helmets, Sports
Bill Barrable on LinkedIn: NFL executive hints that Guardian Caps could eventually be worn in games…
Guardian Cap Results: “Exceeded Our Expectations”
NFL training camps: Guardian Cap players are wearing over helmets, why
2015 Football Media Guide by Army West Point Athletics - Issuu