EC34 headset standard (external cup vs IS41 headset standard (integrated: specs compared
Updated 05 September 2026.
3
specs differ
EC34 headset standard (external cup and IS41 headset standard (integrated differ on 3 specs: shis designation, cup / bearing outside diameter, crown race.
| Spec | EC34 headset standard (external cup | IS41 headset standard (integrated |
|---|---|---|
| SHIS designation | EC34 (external cup (EC)) | IS41 (integrated (IS)) |
| Cup / bearing outside diameter | 34.0 mm cup outside diameter, 33.8 to 33.95 mm head-tube bore | 41.0 to 41.1 mm bearing outside diameter |
| Steerer diameter | 28.6 mm (1 1/8 in) | 28.6 mm (1 1/8 in) |
| Crown race | 30.0 mm crown race seat | 30.0 mm crown race, or machined into the fork |
Questions and answers
How do EC34 headset standard (external cup and IS41 headset standard (integrated compare?
EC34 headset standard (external cup and IS41 headset standard (integrated differ on 3 specs: shis designation, cup / bearing outside diameter, crown race.