Filters listed here are replacement 

Finite (Parker) compressed air inline filter grades PU, QU, CU, and AU represent different levels of purification designed to remove contaminants such as water aerosols, oil aerosols, dust, and oil vapours from compressed air systems. They are part of the H-Series and similar product lines. 

Here is the breakdown of these grades:

• PU (Particulate/Dry Dust Filter): Often used for removing dry particulate matter (dust, rust). It is frequently used for pre-filtration or to remove dry solids, protecting downstream equipment.
• QU (Quality/High-Efficiency Coalescer): A high-efficiency coalescing filter designed to remove oil aerosols and water aerosols. These are typically used for high-purity applications, offering very fine filtration.
• CU (Coalescing/General Purpose): A general-purpose coalescing filter used to remove oil and water aerosols, as well as fine particulates. Often used to protect tools, valves, and instruments.
• AU (Activated Carbon Adsorber): Specifically designed to remove oil vapors and odors. These are used in applications requiring odor-free and vapor-free air, such as in food processing or air breathing.