Football players wear a surprising amount of gear on and inside their helmets beyond the shell itself. From soft protective caps to communication speakers, visors, reward stickers, and impact sensors, modern helmets are loaded with technology and tradition. Here’s what each item is and why it’s there.
Guardian Caps
The most visible addition to football helmets in recent years is the Guardian Cap, a padded shell that fits over the outside of the helmet. It looks like a puffy, oversized cover, and it’s designed to absorb force before it reaches the helmet itself. The NFL made Guardian Caps mandatory during practices for every position except quarterbacks, kickers, and punters starting in 2024. That same season, players were allowed to wear them in games for the first time.
Testing at Virginia Tech’s helmet lab shows measurable benefits. When one player wears a Guardian Cap, concussion risk drops by about 34%, with an 8% reduction in straight-line impact force and a 14% reduction in rotational force (the twisting motion most closely linked to concussions). When both players in a collision are wearing them, concussion risk drops by 63%. Those numbers explain why the NFL pushed the mandate despite early complaints about the caps looking bulky or unfashionable. At the college and high school levels, adoption is growing but not yet required league-wide.
The Green Dot: Coach-to-Player Radio
If you’ve noticed a small lime-green circle on the back of certain helmets, that’s the “green dot.” It signals that the helmet contains a one-way radio speaker, allowing a coach to communicate play calls directly to the player. Only one player per side of the ball can wear the dot at a time. On offense, it’s always the quarterback. On defense, it’s traditionally a linebacker, though some teams have shifted that role to a safety or other defensive back as schemes have evolved.
The system is one-way only: coaches talk, players listen. Communication cuts off when the play clock hits 15 seconds. If a coach tries to speak after the cutoff, a warning tone sounds in the headset. The NFL chose lime green specifically because its operations department determined it was the most visible color for officials and opposing teams to identify.
Visors and Eye Shields
Clear plastic visors attached to the face mask are common across football. They protect against fingers, turf debris, and glare. The NFL allows clear visors freely but restricts tinted ones. The reason isn’t cosmetic: medical staff need to see a player’s eyes quickly after an injury without removing the helmet, and dark tinting makes that impossible.
Players who suffer from migraines or light sensitivity can apply for a medical exemption to wear a tinted visor. Without that exemption, tinted shields draw a penalty. In college football, rules are similar, though enforcement varies by conference.
Helmet Reward Stickers
In college football, small decals on helmets aren’t decorative. They’re earned. Thirteen FBS programs currently use helmet sticker reward systems, and the two most famous are Ohio State and Michigan, whose traditions trace back to the 1960s rivalry between coaches Woody Hayes and Bo Schembechler.
Ohio State’s iconic buckeye leaf stickers were first worn in 1967, inspired by a suggestion from the team’s head athletic trainer, Ernie Biggs. Players start each season with a clean helmet and earn leaves week by week. Every player gets at least one leaf per win. A victory over Michigan is worth three. Stickers are also awarded for standout individual or position-group performances. The presentation happens at Tuesday practice, where head coach Ryan Day calls out names and players shake his hand in what the team treats as a formal “business transaction.”
Michigan’s system works differently. Schembechler originally brought sticker rewards from his time coaching at Miami of Ohio, where his teams wore tomahawk stickers as early as 1965. The tradition continued at Michigan until Lloyd Carr dropped it in 1995. Jim Harbaugh revived it when he returned as head coach in 2015, eventually shifting to a team-based model in 2021. Where Ohio State’s stickers reset each season, Michigan’s helmets are designed to tell the story of a player’s entire career, accumulating different images for different accomplishments year over year.
Impact Sensors
Some helmets, particularly at the college and high school levels, contain built-in sensors that track head impacts in real time. Riddell’s InSite system is one of the most widely used. Sensors inside the helmet measure the force and location of each hit, then transmit that data wirelessly to sideline tablets and reporting dashboards. Coaching and medical staff can see which position groups are absorbing the most contact and identify individual players who may be leading with their head in a dangerous way.
The data isn’t used to diagnose concussions on the spot, but it helps programs spot patterns. If a linebacker consistently registers high-force impacts during a particular drill, coaches can adjust technique or playing time before an injury occurs. Programs subscribe to the analytics service and receive detailed breakdowns over the course of a season.
Mouthguard Sensors and Helmet Pairing
A newer layer of tracking technology sits not on the helmet but in the mouth. Instrumented mouthguards contain sensors that measure how the head moves during an impact, including acceleration and rotational forces. Because the upper teeth are rigidly connected to the skull, a mouthguard pressed against them captures head motion more accurately than sensors attached to the helmet shell or stuck to the skin, both of which can shift independently of the skull during a hit.
These mouthguards are used primarily in research and at some collegiate programs. They generate detailed biomechanical data that helps engineers design better helmets and helps medical researchers understand the specific forces that lead to concussions. While they’re not yet standard equipment, they represent one of the most promising tools for connecting what happens on the field to what happens inside the brain.