This is a bottle of Air Filter Oil from Mugen (B0329).
This is one of the best foam filter oils you can get, and should be massaged into the filter until you get an even pink color. Usually it is best to put the foam filter in a small plastic bag with the oil to make it easy to massage the oil fully into the filter. Before installing on your vehicle, squeeze any excess oil out with a clean rag.
Note: This oil is very thin to allow it to be evenly spread throughout the filter. However when it dries out, it will get thick, so you should make sure you remove all the excess oil from the filter before you let it sit to avoid over oiling the filter.