These sliding dropout plates are compatible with all Boost spaced Big Bro models (2021 and later). The dropouts convert the spacing of the frame from Boost 148mm to 135mm. This allows a Rohloff Speedhub with 10mm axle and OEM axle plate to be fitted (these dropouts may also provide compatibly with other internally geared hubs).
Please note: these will not work with the older non-Boost Big Bro framesets (pre-2021).