Kids · Boys'
Size-matched helmets for 9 year olds, with color and style notes typically preferred by boys in this age range. Fit remains the priority - pattern and color second.
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Bell
S 52-56 cm, M 56-60 cm, L 60-64 cm

Giro
S 51-55 cm, M 55-59 cm, L 59-63 cm

Joystar
Adjustable dial-fit kids multi-sport helmet sized for ages 3-8. Compatible with biking, skateboarding, and scooter use. EPS foam with vented hard shell.
Kask
S 50-54 cm, M 54-58 cm, L 58-62 cm

Mongoose
Multisport kids helmet built for ages 5-8. Microshell shell stays light enough for skateboarding and scooter use, while the internal pads and adjustable dial keep it snug as kids grow.

Poc
S 50-54 cm, M 54-58 cm, L 58-62 cm

Royalbaby
Designed for kids ages 5-13. Adjustable dial accommodates a growing child without needing a new helmet each season. Pair with the matching knee/elbow set for first-time riders.

Schwinn
Sized for toddlers ages 1-3 with 44-50 cm head circumference. Adjustable dial and full-range padding give a snug fit as the child grows.

Smith
S 51-55 cm, M 55-59 cm, L 59-63 cm

Troy Lee Designs
S 53-56 cm, M 56-59 cm, L 59-62 cm

Woom
Sized by head circumference (inches). XS: 18.2"-19.6" (ages 1-3), S: 19.7"-20.8" (ages 3-7), M: 20.9"-22" (ages 7-14). Multiple colorways available.

Poc
XS/S 51-54 cm, M-L 55-58 cm, XL/XXL 59-62 cm
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Nine-year-olds are prime 24" bike riders. Children this age have the strength, coordination, and confidence to ride more serious bikes with gears, hand brakes, and sometimes front suspension. The proper fit at this age shifts slightly toward a more active position - the child should be able to touch the ground with the balls of their feet (or even just toes for experienced riders) when seated. A 1x7 or 1x8 drivetrain is standard for 24" bikes and handles everything from neighborhood cruising to trail riding. Disc brakes are increasingly common and worth choosing for better all-weather stopping power. Bike weight matters but is less critical than for younger children - aim for under 12 kg.
Measure head circumference at the widest point across the forehead. Most brands size: XS (50-53 cm), S (53-56 cm), M (56-59 cm), L (59-62 cm), XL (62+ cm). Kids helmets typically start at 47-50 cm. Always try before buying; fit varies by brand.
Cross-shop the helmets 9 year olds actually consider - specs, fit, and the deciding factor.
Two sub-$100 MIPS helmets from the category's biggest brands - the road-leaning Giro Register versus the MTB-ready Bell Nomad. Picking the right one comes down to where you ride, not the price tag.
Two premium road helmets the WorldTour actually wears - Team Sky's Kask Protone Icon versus EF's POC Omne Air SPIN. Both ~160 g, both well-vented, but the rotational-impact tech and aero shape are very different.