Right side from the back (Part No: 007289): This is the filter and moisture/water trap, and you can distinguish it by the presence of the black tapered drain valve at the bottom of the bottle to automatically or manually drain the accumulated water. Left side from the back (Part No: 008211): This is the lubricator, and above it clearly appears the transparent glass dome (oil drop flow indicator) with the blue adjustment knob next to it to control the amount of lubrication, and below the bottle it is closed and round without a drain valve. Middle part (Part No: 009186): This is the body of the upper pressure regulator, and it contains side mounting holes for installing the device on the wall or on the compressor body itself.