A chain guide bolts to the frame's ISCG tabs (or clamps the bottom bracket when there are none). The tab standard is rarely printed on a complete-bike spec sheet, so most 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.