Diaphragm Cb750k7 Four (england)

It really is worth replacing this item whenever you service or overhaul your braking system, it does not cost much, and even a barely visible pin prick may allow air bubbles to form and give the impression of spongy brakes!
For the rest of your brake components and consumables, take a look at the online 'parts list' fiche for your model, and specify a multiple order for all the parts you need to complete the job. Ultimately saving money on shipping costs, and time in your garage, when you find you overlooked a small but essential component!