The Problem: The Porsche® 928 is fitted with a Master Cylinder cap that is vented. This causes two problems:
The Solution: This top gasket for your stock brake fluid cap uses a bellows instead of a vent to seal your master cylinder, yet allow for the expansion and contraction of the fluid in the reservoir as per normal use. This is the way all modern vehicles close their master cylinders now - no air is allowed to contact and corrupt the fluid, and no fluid is allowed to escape wrecking your paint job (brake fluid is an excellent paint remover).
Installs in Less than 1 Minute: Installs into your stock brake master cylinder reservoir cap. Remove the cap, remove the old vent and gasket, install the new bellows, re-install the gasket, and put the cap back on your master cylinder. Done. Instructions are included and ship with the bellows.