This is the exact same cup assembly currently installed by Fuji on their standard spray guns. The assembly includes the 2024 Pressure Tube, a fitted 2036 Gasket and 2038 Diaphragm. It is the diaphragm that helps prevent paint entering the pressure tube. It acts as a shield. The standard cup assembly is supplied with no coating on the inside. This can be used with all products although some water-based coatings can cause an unsightly staining inside the cup (usually harmless and never affecting the actual finish).