1977 Honda CB550K Master Cylinders & Reservoir Parts

It is the piston size of the offered assembly, and its description asks buyers to confirm the fitted size. Identify the cylinder on your motorcycle before using that product specification to choose replacement internals or a complete unit.

The description says it has no mirror mount and separately lists the brake switch, banjo bolt and washers. Compare the universal unit with the fitted control arrangement and identify those additional pieces before completing the order.

The kit description gives 45530-404-315 and lists CB550K 1977–78. Compare that application and reference with the actual master cylinder, especially if the fitted unit is a replacement whose internal kit requirement is uncertain.