Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post
Guardian Cap debuts during minicamps in effort to reduce avoidable head contact
Guardian Cap: What are and why the NFL asks this safety measure in helmets
So what exactly is that black padding on the Syracuse football helmets seen during practice?
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
NFL introduces Guardian Caps across league to limit number of brain injuries in preseason
Cam Rising Will Be Wearing New Technology Helmet In 2022
Guardian Cap - Soft-Shell Protective Helmet Cover : Football Helmets : Sports & Outdoors
What are those caps football players are wearing?
Guardian cap' to prevent head injuries mandated for practices, CFL says
Can a Better Football Helmet Save Your Kid's Brain? - Washingtonian