Why are NFL players wearing padding on helmets at training camp?
These puffy helmet caps are the next big thing in NFL player safety, National Sports
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
NFL expands rule against misuse of helmet; Guardian Caps required in regular season, postseason
Guardian Caps: NFL requires use of helmet cover at training camps to reduce head injuries
Guardian Caps: The new helmets worn by several NFL teams
NFL commissioner Roger Goodell believes football will become safer
NFL's use of Guardian padded helmet caps in camp draws support and skepticism - The Athletic
Get A Load Of These Big Dumb Helmet Helmets