Guardian Caps: The new helmets worn by several NFL teams
NFL training camps: Guardian Cap players are wearing over helmets, why
Padded helmet cover shows little protection for football players - Scope
Steelers debut new, safer helmets for off-season training
Guardian Cap Use a Concern for Watt, Saleh Early in Training Camp - Sports Illustrated
NFL mandates use of Guardian Caps for training camp in 2022 - Cincy Jungle
Guardian Caps Debut at Training Camps Across the NFL
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
Guardian Caps Guardian Sports
Eagles Notes: New Guardian Caps get mixed reviews – Delco Times
Guardian Cap debuts during minicamps in effort to reduce avoidable head contact
NFL players wear Guardian Caps to reduce head trauma during training camp