EC44 headset standard (external cup, 44 mm)
What a EC44 headset measures under the SHIS standard, and how to tell it apart from lookalikes.
Published dimensions
| SHIS designation | EC44 (external cup (EC)) |
|---|---|
| Cup / bearing outside diameter | 44.0 mm cup outside diameter, about 43.9 mm head-tube bore |
| Steerer diameter | 28.6 mm upper (1 1/8 in) or 38.1 mm lower (1 1/2 in) crown race |
| Crown race | 30.0 mm upper crown race, 40.0 mm lower crown race |
Used on: the lower cup of a tapered 44 mm head tube, and some external 1 1/8 in uppers.
EC44 shares the 44 mm bore of ZS44 but the bearing sits in a cup outside the head tube, so an EC44 cup is taller than a ZS44 one. A 44 mm head tube can take EC44 or ZS44, so measure whether the bearing sits inside or outside the tube.
Frames and related headsets
EC34external cup, 34 mmEC49external cup, 49.6 mmZS44zero stack, 44 mmZS55zero stack, 55 mmIS41integrated, 41 mmBSA bottom bracket shellthe frame's other threaded interface
SOURCES: White Industries, ZS44/EC44 headset · Park Tool, Standardized Headset Identification System (SHIS)