The measured head circumference decides the size, not the S/M/L label
Helmet sizes are sold as S/M/L but fitted by head circumference in centimeters, and the ranges behind those letters differ enough between makers that the same nominal size can be two centimeters apart. We compare the circumference range each manufacturer states, how the retention cradle adjusts (dial systems allow finer changes than a sliding band, and only some adjust in height as well), vent count, integrated lighting, and the safety marking the maker declares — EN 1078 in Europe, and CPSC, ASTM F1447 or CE on the helmets sold here. One helmet on this page publishes its own weight, 260 g (9.2 oz); for the others only a shipping weight exists, which includes the box. That marking is a manufacturer statement we report; nothing on this page assesses how a helmet performs in a crash.
54–59 cm (21.3 to 23.2 in) · 16 vents · integrated rear light
The best-selling helmet in this hub, with an EPS inner shell, sixteen vented inlets with insect mesh and an integrated three-mode rear light built into the retention ring.
Best for: Everyday town riding where being seen matters as much as anything else.
58–62 cm (22.8 to 24.4 in) · CPSC extended head coverage · 20 or 21 vents · dial · removable visor
A recreational adult helmet covering 58 to 62 cm (22.8 to 24.4 in) from one shell, with a dial, washable padding and a removable visor.
Best for: A large head, or a cheap certified helmet for recreational riding
56–59 cm (22 to 23.2 in) · height-adjustable cradle · Multi-Fit light
A touring helmet from an established German sports brand, with a height-adjustable retention cradle, insect mesh in the front vents and a high-mounted integrated light.
Best for: Longer rides where a cradle that adjusts in two axes makes the difference over several hours.
58–61 cm (22.8 to 24 in) · 6 LEDs, 3 modes · removable visor
A size L helmet for 58–61 cm (22.8 to 24 in) heads with six rear LEDs in three modes, a removable visor and a dial adjuster, supplied with the CR1620 cell already fitted.
Best for: Riders with a larger head who want lighting and a visor without moving up in price.
59–61 cm (23.2 to 24 in) · double in-mold PC shell · 20 mm (0.79 in) EPS
A mountain bike helmet with a double in-mold polycarbonate shell over 20 mm (0.79 in) EPS foam, a longer visor, and a rear band designed to hold glasses.
Best for: Trail riding where mud, branches and low sun are the everyday nuisances.
M 54–58, L 58–61, XL 61–63 cm (24 to 24.8 in) · CPSC, ASTM F1447, CE · 18 vents · big visor
A mountain bike helmet in three published size bands, with eighteen channelled vents, a polycarbonate shell fused to EPS and three declared markings.
Best for: A trail rider with a measured head between 54 and 63 cm (24.8 in) who wants the standard named
Adult MTB · PVC, PC and EPS · large lifting visor · one-hand dial
An adult mountain bike helmet in PVC, polycarbonate and EPS, with a large sun visor that moves upward and a one-handed dial.
Best for: A rider who wants a visor that flips up, and will ask the seller for the size
58–60 cm (22.8 to 23.6 in) (L) · 260 g (9.2 oz) published · 26 vents · CPSC, ASTM and CE · in-mold EPS
A 260 g (9.2 oz) commuting and road helmet in 58 to 60 cm (22.8 to 23.6 in), with twenty-six vents, in-mold EPS construction and three declared safety markings.
Best for: A commuter who wants a light certified helmet and a measured 58 to 60 cm (22.8 to 23.6 in) head
Size M · MIPS · two liners, 5.8 and 7.9 mm (0.31 in) · 25 vents · removable visor
A MIPS recreational cycling helmet in size M with two interchangeable liner thicknesses, twenty-five vents and a removable visor.
Best for: A head between sizes, or a rider whose glasses foul the helmet edge
21 vents · USB rear light · magnetic detachable goggles
The most equipped helmet in this hub: twenty-one vents, a USB-rechargeable rear light with three modes, and detachable magnetic goggles that double as sunglasses.
Best for: Trail riders who want ventilation, light and eye protection in one purchase rather than three.
Medium · Integrated MIPS · Roc Loc 5 · hardshell with in-mold lower wrap
Giro’s Agilis in Medium, with Integrated MIPS, the Roc Loc 5 fit system and a two-piece hardshell fused to its EPS liner.
Best for: A road rider who wants the fit adjusted in two axes and will measure before ordering
A helmet only protects if it is the right size and properly adjusted. Head circumference is the one measurement that decides, before any other consideration.
A helmet that is too big moves at the moment of impact and no longer protects the area it was meant to cover. Small sizes exist for that reason.
A hundred grams more tell on the neck after three hours, not in the first kilometer. The weight stated for the actual size, not for the smallest, is what to compare.
By measuring head circumference with a tape, above the eyebrows. Size comes before everything else: a badly adjusted helmet does not protect as it should.
Level on the head, two fingers above the eyebrows, dial tightened, straps forming a V under the ears and the chin strap leaving room for one finger.
Yes, every time, even with no visible damage. The foam absorbs the impact by deforming irreversibly and invisibly.
Manufacturers generally state a period after which the materials age. Sun and heat accelerate that aging.
Every compliant helmet meets the same requirement. The price buys comfort, ventilation and lightness.
It is for under-twelves in France, riders and passengers alike. Above that age it is strongly recommended without being compulsory.
It is inadvisable: nothing says it has not taken an impact. A helmet that has absorbed one does not show it.
Lukewarm water and mild soap, never a solvent, which attacks the foam. The inner pads come out and can be washed on most models.
Size and fit decide everything: a helmet that moves does not protect the area it was meant to cover. Replace it after any impact, even with no visible damage — the foam has deformed irreversibly — and never buy one second-hand.
There is no table here, and the reason is in the listings. The figure published most often across these 11 products is price, given by 6 of them — short of the four in five a column needs to compare rather than to display gaps. Each product page says what its own maker published.
Specifications: manufacturer sheets for bike gear and the matching Amazon product pages. Prices and availability: Keepa.
Most recent revision in this category: October 6, 2026.
Prices quoted in these summaries are dated readings. The live price is shown next to each product.
