Why are NFL players wearing padding on helmets at training camp?
What is on Drue Tranquill's neck? Chargers LB spotted wearing Q-Collar to limit head trauma
Large Bubble Helmets Are Guardian Caps, NFL's New Safety, 45% OFF
Guardian Caps leave some NFL players and coaches with concerns: 'You feel like a bobblehead'
Players, coaches react to mandatory use of Guardian Caps
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
Xenith Shadow XR Top-Rated Varsity Football Helmets Xenith
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post
EXPLAINER: NFL using helmet caps for player safety, research