Here's why some Patriots players are wearing caps over their helmets during training camp
What are Guardian Caps? NFL's latest padded helmets for added safety
So what exactly is that black padding on the Syracuse football helmets seen during practice?
LSU football reveals new air-conditioned helmets drawing rave reviews from players
Bengals Training Camp Report: Vonn Bell Mentors Dax Hill
NYSportsJournalism.com - NFL Guardian (Caps) Of The Preseason Galaxy - Safety Impact: NFL Expands Presence As Guardian (Caps) Of The Preseason Galaxy
NFL training camps: Guardian Cap players are wearing over helmets, why
Eagles players on Guardian Caps: 'We look a little goofy,' but all for safety
What is the NFL Guardian Cap? Will it do anything to reduce concussion? — Dr. Mark Heisig
EXPLAINER: NFL using helmet caps for player safety, research
NFL concussions Guardian Cap - TSN.ca
Why are NFL players wearing padding on helmets at training camp?