Steelers debut new, safer helmets for off-season training
NFL hopes to reduce head injuries with helmet experiment
NFL players wear Guardian Caps to reduce head trauma during training camp
EXPLAINER: NFL using helmet caps for player safety, research
Eagles players on Guardian Caps: 'We look a little goofy,' but all for safety
For Giants and the NFL, it's the Summer of Guardian Caps - Newsday
Why are NFL players wearing padding on helmets at training camp?
NFL players beginning to adopt protective Guardian Caps over helmets at practice - NBC Sports
Saints adjusting to use of Guardian Caps in training camp - Daily Leader
NFL players experiment with 'Guardian Caps' to protect heads