A seat collar fits the outside of the seat tube, not the post: the number printed on it is the tube diameter. Few spec sheets state it, which is why many bikes read "unknown" here.
- How do I know whether a part in this category fits my bike?
- Every part page lists the standards it requires and its computed verdict on each bike in the fleet, with its confidence and sources. An "unknown" verdict means we do not have the measurement on file — not that it fits.