7iDP Bike Helmet Size Chart





7iDP Mountain Bike Helmets Standard Sizing

Model Youth Medium Youth Large X-Small Small Medium Large X-Large XX-Large
M1 Helmet 48 – 50cm 50 – 52cm 53 – 54cm 55 – 56cm 57 – 58cm 59 – 60cm 61 – 62cm
18.8″ – 19.6″ 19.6″ – 20.5″ 20.75″ – 21.25″ 21.5″ – 22″ 22.5″ – 22.75″ 23.5″ – 23.75″ 24″ – 24.25″
Project 23 ABS

53 – 54cm 55 – 56cm 57 – 58cm 59 – 60cm 61 – 62cm 63 – 64cm


20.75″ – 21.25″ 21.5″ – 22″ 22.5″ – 22.75″ 23.5″ – 23.75″ 24″ – 24.25″ 24.8″ – 25.2″
Project 23 Carbon

53 – 54cm 55 – 56cm 57 – 58cm 59 – 60cm 61 – 62cm 63 – 64cm


20.75″ – 21.25″ 21.5″ – 22″ 22.5″ – 22.75″ 23.5″ – 23.75″ 24″ – 24.25″ 24.8″ – 25.2″
Project 23 Fiberglass

53 – 54cm 55 – 56cm 57 – 58cm 59 – 60cm 61 – 62cm 63 – 64cm


20.75″ – 21.25″ 21.5″ – 22″ 22.5″ – 22.75″ 23.5″ – 23.75″ 24″ – 24.25″ 24.8″ – 25.2″

7iDP Mountain Bike Helmets Sizing #2

Model X-Small / Small Medium / Large X-Large /
2X-Large
M2 Helmet 52 – 55cm 56 – 59cm 60 – 63cm
20.5″ – 21.75″ 22″ – 23.25″ 23.75″ – 25″

7iDP Mountain Bike Helmets Sizing #3

Model Small /
Medium		 Large /
X-Large
M5 Helmet 54 – 58cm 58 – 62cm
21.25″ – 23″ 23″ – 24.5″