Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
Why Utah players wore Guardian Caps during camp - Deseret News
Here's why some Patriots players are wearing caps over their helmets during training camp
The story behind those soft-shell puffy Guardian Caps players have been wearing
Cowboys seen wearing protective, NFL mandated Guardian Caps at OTAs
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
Here's why some Patriots players are wearing caps over their helmets during training camp
Large Bubble Helmets Are Guardian Caps, NFL's New Safety Measure