NFL players wear Guardian Caps to reduce head trauma during training camp
What Pros Wear: Guardian Caps What are Those Helmet Covers Being Worn in Practice? - What Pros Wear
NFL hopes to reduce head injuries with helmet experiment
More Guardian Caps, And '0' On The Field
Guardian Caps', NFL's Most Recent Attempt At Preventing Head Injuries
CFL introduces mandatory extra helmet protection for multiple positions. As well as other new health & safety measures. : r/sports
Arizona Cardinals defensive end J.J. Watt not fan of the new league-mandated Guardian Caps on helmets
With increasing knowledge of CTE, parents are now faced with tough decisions when it comes to youth football – New York Daily News
Guardian Caps Guardian Sports
With a little imagination NFL's new Guardian Caps take on different look in Cleveland: Crowquill
EXPLAINER: NFL using helmet caps for player safety, research
Xavier Woods returns to his football sanctuary
What is the NFL Guardian Cap? Will it do anything to reduce concussion? — Dr. Mark Heisig
Colin Kaepernick - Wikipedia