Guardian Caps: Why some NFL players are wearing them in training camps
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
NFL Expands Use Of Guardian Caps In 2023 - Steelers Depot
Here's why some Patriots players are wearing caps over their helmets during training camp
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With a little imagination NFL's new Guardian Caps take on different look in Cleveland: Crowquill
Why are NFL players wearing padding on helmets at training camp?
What are those funny-looking soft caps on NFL helmets during camp?, Sports
NFL Players Experiment With 'Guardian Caps' to Protect Heads – NBC Connecticut