Stilo ST6 Rally Composite Helmet – White

Helmet letters mean less here than anywhere else on the site. At 58 cm round the head you are a Bell M, a Sparco M and an Arai M, but a Stilo L and a Schuberth L. Measure once, then read your own number off the chart for the brand you are buying.

Measure your head

Bell put it best on their own guide, and every brand here measures the same way. Take the circumference about an inch above your eyebrows at the front, and at whatever point at the back gives you the biggest number. Take it three or four times and use the largest reading.

Your size in every brand we stock

Find your measurement in the left column. A dash means that brand does not make a size at that measurement, not that it is out of stock.

Sparco column is the Stealth RF ladder, which is what almost everything we stock from them uses. OMP column is the GP-R. Bell HP/Pro covers their HP, Carbon and Pro models, which use a different chart from the rest of the Bell range.

What catches people out

Bell run two different charts

Bell publish one chart for most of the range and a second for the HP, Carbon and Pro models. They are not the same. On the general chart a 56 cm head is an XS; on the HP, Carbon and Pro chart the same head is an S. That is why some Bell helmets on the site are sold as S, M, L and others as 54cm, 55cm, 56cm and so on up to 61+. The numbered ones are the HP, Carbon and Pro models and you pick your measured size directly.

Stilo run small, and skip some sizes

Stilo say it themselves: their helmets “run traditionally a hair smaller than other sizes on the market”. On top of that the ST6 ladder steps unevenly, so 56, 60 and 62 cm have no size of their own. If you measure at one of those, or you are on a boundary anywhere in the Stilo range, go up rather than down and ring us first.

A shell size is not a helmet size

Every brand here builds a handful of outer shells and then changes the padding inside to make the sizes. Going up a size inside the same shell costs you nothing in bulk or weight. Crossing into the next shell up makes the helmet visibly bigger and noticeably heavier, which you feel over a long stint and which matters if you are tight for room in the car.

Shell splits published by Stilo and Schuberth. Arai build more outer shells than anyone else here and also offer different shell shapes for rounder and longer heads, which is worth knowing if other brands have never quite fitted you.

Full charts by brand

How a helmet should fit

Tight, then tighter than you think

A new helmet should be snug enough that it is slightly awkward to pull on, and the cheek pads should push your cheeks up. The lining compresses with use, so a helmet that is merely comfortable in the showroom will be loose by the end of the season. Do the roll-off test: with the strap done up, take the back of the helmet and try to rotate it forwards off your head. If it moves, it is too big.

Open face and full face are not the same fit

An open face sits differently because there is no chin bar pulling the shell forward, and several brands build their open face range on a separate set of shells. If you are moving from one to the other, do not assume your size carries across. Stilo in particular build the Venti open face on three shells and the ST full face on two.

Glasses

Say so when you order. Some models take a glasses channel in the cheek pads and some do not, and it is much easier to sort out before the helmet ships than to feed the arms in afterwards.

Bell from bellracing.com. Stilo shell and fit information from stilohelmets.com. Sparco generic chart via Racecar Engineering, model ladder from the range we stock. Arai from whyarai.co.uk. Schuberth from their published SF4 and SP1 data. Zamp and OMP from the sizes on the products themselves. All checked 2 August 2026. If the chart in the box disagrees with this page, the box wins and we would like to know.