So what exactly is that black padding on the Syracuse football helmets seen during practice?
NFL Is Considering A 'Potential Change' To Its One-Helmet Rule For 2021 Season
Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post
Arizona Cardinals defensive end J.J. Watt not fan of the new league-mandated Guardian Caps on helmets
Types of Padding in Football Helmets - SportsRec
NFL Media's Steve Wyche: How NFL's helmet technology has taken off in 2022
EXPLAINER: NFL using helmet caps for player safety, research
For Various Reasons, N.F.L. Players Do Not Wear Cups - The New York Times
What are the padded helmets players are wearing at NFL training camps?
Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
NFL's use of Guardian padded helmet caps in camp draws support and skepticism - The Athletic