Genuine AP reproduction 3 port pressure limiter valve for all Mk3 on to the end of the single line master cylinder system, where it was replaced with a simple tee. This was fitted from 1970 on standard models, but the Mk3 Cooper "S" and some other special 1970-78 models still used the earlier type (21A1774). This valve is fitted on the rear subframe and reduces rear brake pressure to the rear brakes, and also acts as the tee.