EXPLAINER: NFL using helmet caps for player safety, research
For Various Reasons, N.F.L. Players Do Not Wear Cups - The New York Times
Guardian Caps: Why some NFL players are wearing them in training camps
NFL players wear Guardian Caps to reduce head trauma during training camp
How the NFL plans to play a season during the pandemic
NFL CMO Dr. Allen Sills explains importance of mandated guardian caps during training camp
Guardian Cap Debuts at NFL Training Camps League-wide
Why are NFL players wearing padding on helmets at training camp?
EXPLAINER: NFL using helmet caps for player safety, research
Padded helmet cover shows little protection for football players - Scope
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Large Bubble Helmets Are Guardian Caps, NFL's New Safety Measure
NFL: Concussions dropped by more than 50% among players who wore Guardian Caps during summer