A Nukeproof Reactor uses a 34.9 mm class seatpost interface. The dimensions, how to confirm it on your frame, and how it compares to the neighbouring standards.
Updated 05 September 2026.
What seatpost diameter does a Nukeproof Reactor use?
The seatpost fitment standard on a Nukeproof Reactor, and how to pick the right part.
| Frame | Nukeproof Reactor |
|---|---|
| Seatpost diameter | 34.9 mm |
| Diameter | 34.9 mm |
| Typical class | modern trail and enduro mountain frames wanting the largest, stiffest dropper interface |
The Nukeproof Reactor uses a ZS44 zero-stack upper headset (zero stack, 44 mm), a 34.9 mm class seatpost, a 15x110 mm Boost front thru-axle at the front (15 mm x 110 mm Boost, front) and a braze-on front derailleur.
Most builds are 1x, so the front-derailleur mount note applies only to 2x setups. The rear is typically Boost 12x148; confirm your generation. The bottom bracket is covered on its own page.
SOURCES: BikeGremlin, Seatpost diameter sizes (standards) · BikeRadar, Bike seatposts explained: diameters, materials, lengths · Park Tool, Standardized Headset Identification System (SHIS) · BikeRadar, Mountain bike axle standards: the complete guide
Questions and answers
What seatpost diameter does a Nukeproof Reactor use?
A Nukeproof Reactor uses a 34.9 mm class seatpost interface.