CHARLOTTE, N.C. (AP) — Five NFL teams are using a product called Guardian Caps to help cut down on the impact of blows to the head in practice.

The 11-ounce soft-shell cover retrofits to the top of a player's helmet and is designed to decrease blows to the head by 10%, thus limiting head injuries. Currently more than 100 players are wearing them, according to Jeff Miller, the NFL’s executive vice president of communications for public affairs and policy.

The caps are currently only used in practices, but it's possible you could see players wearing them in games in the future.