Steelers debut new, safer helmets for off-season training
NFL hopes to reduce head injuries with helmet experiment
The story behind those soft-shell puffy Guardian Caps players have been wearing
Ravens Embrace the Funny-Looking Guardian Helmets - Sports Illustrated Baltimore Ravens News, Analysis and More
Eagles players on Guardian Caps: 'We look a little goofy,' but all for safety
What Pros Wear: Guardian Caps What are Those Helmet Covers Being Worn in Practice? - What Pros Wear
So what exactly is that black padding on the Syracuse football helmets seen during practice?
Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post
Soft Protective Headgear Buy Soft Shell Helmets & Protective Padded Equipment Online - GameBreaker
Built By Data: NFL Helmet Innovation
The Fruitless Search for a 'Concussion-Proof' Football Helmet - The Atlantic
Football helmets with outside padding get tryout at high schools