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SKU: zs44zs44
Clear Options


The ZS44│ZS44 headset is designed to fit frames with straight 44mm head tubes and only works with straight 1-⅛” (28.6mm) fork steerers.  The “ZS” stands for “Zero Stack” as the section of the cup that houses the bearing sits inside of the frame’s head tube.  The “44” stands for the diameter of the “skirt” that presses into the frame.

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 “Straight 1-⅛” steerers with a 30mm crown race seat
  • Compatible with Ritchey carbon 1-1/8″ steerer forks with integrated crown races (not tapered steerer forks)
    • Must purchase additional bearing part #ACB45451125TSS (Parts>Headset Parts) which replaces the stock bearing and crown race
      • WCS road SKU 34356117005
      • WCS road SKU 34356117006
      • WCS Adventure Gravel SKU 34556117012
      • WCS Gravel Cross SKU 34556117010


  • SHIS specification
    • Upper: ZS44/28.6
    • Lower: ZS44/30
  • Stack height
    • Upper: 8mm
    • Lower: 4mm
  • SHIS definitions on the Park Tools website: here
  • Frame/Fork specs:

Frame upper head tube inside diameter

43.95mm to 44mm

Frame lower head tube inside diameter

43.95mm to 44mm

Fork steerer diameter top section 

28.45mm to 28.6mm

Crown race seat diameter for

“straight 1-⅛”

30.015mm to 30.075mm



Headset Model

Upper Bearing (inner/outer angle) Lower Bearing 

(inner/outer angle)

Lower Fork Race Compatibility


ACB3645SS 36/45 ACB3645SS 36/45

1-⅛” (30mm)


Additional information

Weight N/A
Dimensions N/A
Head Tube

Top Steerer

Bottom Steerer / Crown Race