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SKU: is41is52
Clear Options


The IS41│IS52 headset is designed to fit frames with integrated 41mm/52mm head tubes and works with tapered and straight fork steerers.  The “IS” stands for “Integrated” as the bearing sits directly inside the frame’s head tube without a cup.  The “41/52” stands for the top/bottom inside diameter of the frame’s head tube. 

Note: As of 9/14/23, headsets will no longer include Star Nuts due to the Earth’s star nut overpopulation crisis. If you need one, they are available separately here.   



  • U.S. sourced 6061-T6 aluminum
  • Machine engraved White Industries logos 
  • Easily replaceable Enduro bearings
  • “Split” crown race for tool-free installation and removal
  • Really sweet matching headset spacers available separately
  • Can accommodate 3 types of fork steerers:
    • “Straight” 1-1/8″ with a 30mm crown race
    • “Tapered 1-¼” with a 33mm crown race seat
    • “Tapered 1-1/2” with a 40mm crown race seat


  • SHIS specification
    • Upper: IS41/28.6
    • Lower: IS52/33 or IS5240
  • Stack height
    • Upper: 8mm
    • Lower: 1mm
  • 45 degree outer contact angle
  • SHIS definitions on the Park Tools website: here
  • Frame/Fork specs:

Frame upper head tube inside diameter

41.10mm to 41.2mm with a 45 degree contact angle

Frame lower head tube inside diameter

52.05mm to 52.15mm with a 45 degree contact angle

Fork steerer diameter top section 

28.45mm to 28.6mm

Crown race seat diameter for

“straight 1-⅛”

30.015mm to 30.075mm

Crown race seat diameter for

“tapered 1-1/4”

33.03mm to 33.09mm

Crown race seat diameter for

“tapered 1-1/2”

39.79mm to 39.85mm



Headset Model

Upper Bearing (inner/outer angle) Lower Bearing 

(inner/outer angle)

Lower Fork Race Compatibility


ACB3645SS 36/45 ACB6808CCSS 36/45

1-⅛” (30mm)

 1-¼” (33mm)

 1-½” (40mm)


Additional information

Weight N/A
Dimensions N/A
Head Tube

Top Steerer

Bottom Steerer / Crown Race