Stilo has two separate shell sizes for this helmet. This allows us to make a better-fitting helmet that is lighter weight. Instead of filling a very large shell with lots of padding for a size small, we have one shell size for x-small to medium, and one for large and x-large. Snell SA2015 vs 2020 …what's changed? The Snell SA2020 testing requirements have changed a small amount and have now become more in line with the FIA 8859 Helmet Standard. Details: Increased velocity by 5-10% for impact testing on the 2nd hit across all shell sizes. Increased velocity from 5.7 to 6.0 m/s on the 54cm to 59cm size. Increased peak G threshold on the 54cm to 59cm size and 60cm-64cm size. Additionally Stilo has made an improvement on the SA2020 Carbon Helmets: SA2020 ST5 Carbon FIA8859 helmets will be 50/60g lighter thanks to our new Puro Super Smooth technology unique to Stilo. This superior finish removes the need for lacquer, and also saves weight. A benefit to painters is the decal is no longer under the clear coat. This model now comes with a decal like our Zero's and 8860's.