Guardian Cap Debuts at Training Camps League-wide
Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
Reduces impact up to 33% One size fits all Insulates in hot & cold weather Fits both football and lacrosse helmets Connects to the facemask with 4
Guardian Protective Helmet Cover
Guardian Cap: What are and why the NFL asks this safety measure in helmets
What Pros Wear: Guardian Caps What are Those Helmet Covers Being Worn in Practice? - What Pros Wear
What are those caps football players are wearing?
Guardian Cap Results: “Exceeded Our Expectations”
Guardian Cap - Soft-Shell Protective Helmet Cover : Football Helmets : Sports & Outdoors
More padding the issue of concussions and better helmets
Football helmet - Wikipedia
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
Guardian Cap Debuts at Training Camps League-wide
What is a Guardian Cap? Meet the NFL's newest safety measure
Guardian Cap Use a Concern for Watt, Saleh Early in Training Camp - Sports Illustrated