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F01012100-110-001

509 Altitude 2.0 Offroad Helmet

Size Guide
509 Sizing Chart

How to Measure

Head: Measure circumference of head just above top of ears and eyebrows.

Waist: Measure under arms, around the fullest part of the chest. Keep tape level across back, comfortably loose.

Chest: With arm fully extended, measure center back of neck at the spine to the wrist bone.

Chest: Measure under arms, around the fullest part of the chest. Keep tape level across back, comfortably loose.

Inseam: Without shoes, measure inside of leg, from groin to floor.

Helmet Sizing US Hat Size Inches Centimeters
X-Small

6 5/8 - 6 3/4

20 7/8 - 21 1/8

53 - 54

Small

6 7/8 - 7

21 5/8 - 21 7/8

55 - 56

Medium

7 1/8 - 7 1/4

22 1/2 - 22 5/8

57 - 58

Large

7 3/8 - 7 1/2

23 1/4 - 23 1/2

59 - 60

X-Large

7 5/8 - 7 3/4

24 - 24 1/4

61 - 62

2X-Large

8

24 3/4 - 25

63 - 64

3X-Large

8 3/4

25 1/4 - 25 3/4

64 - 65

4X-Large

9

26 - 26 1/4

66 - 67


Youth Helmets US Hat Size Inches Centimeters

Youth Small

6

18 1/8 - 18 7/8

47 - 48

Youth Medium

6 1/8 - 6 1/4

19 1/4 - 19 5/8

49 - 50

Youth Large

6 3/8 - 6 1/2

20 - 20 1/2

51 - 52


Men's Sizing X-Small Small Medium Large X-Large 2X-Large 3X-Large

Chest

34 - 36

36 - 38

39 - 41

42 - 44

45 - 47

48 - 50

52 - 54

Sleeve

27

28

30

32

34

36

36

Waist

30

32

34

36

38

40

42

Inseam

29

30

31

32

33

34

34

Short Inseam

29

29

30

30

31

31

31

Tall Inseam

34

34

35

35

36

36

36

Gloves

7

8

9

10

11

12

13


Women's Sizing X-Small Small Medium Large X-Large 2X-Large

Chest

30

32

34

36

38

40

Sleeve

24

26

28

30

32

34

Waist

28

30

32

34

36

38

Inseam

29

30

32

34

36

38

Gloves

5

6

7

8

9

n/a

Want to know more about the availability of this product?

509 Altitude 2.0 Offroad Helmet

Reinvented to ride even harder, the second generation of the bestselling 509 Altitude series unleashes a whole new animal. For those who run at redline, the new 509 Altitude 2.0 Hi-Flow Helmet maximizes airflow with open upper and rear vents plus a 40% larger chinbar intake. Everything else is what you’d expect from one of the world’s bestsellers, including a new hand lay-up fiberglass construction that makes this helmet lighter, stronger, . . . Show More >

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