NFL players don Guardian Caps, designed to protect from concussion
For Various Reasons, N.F.L. Players Do Not Wear Cups - The New York Times
Patriots, rest of NFL wearing cushioned helmet caps at training camp, per new mandate - CBS Boston
Patriots Mailbag: Which RB makes sense, looking for OL depth and other camp musings
Steelers debut new, safer helmets for off-season training
NFL hopes to reduce head injuries with helmet experiment
Broncos' new Snowcapped helmets a nod to storied past
What's With Those Padded Caps NFL Players Are Wearing In Training Camp?
NFL says positions wearing Guardian Caps saw 52% decrease in concussions - NBC Sports
Guardian Caps: NFL requires use of helmet cover at training camps to reduce head injuries