This is a 40cc bottle of Kyosho 2,000wt (#2000) Silicone differential oil for 1/8th scale off road buggies (and some 1/10th scale on-road touring cars). The thicker the oil, the less your differential will "diff out" in the corners, where the two tires will turn at different speeds. Changing the diff oil in your diffs is one of the most important tuning options for off-road buggies.
NOTE: It is not recommended to mix oils of different brands, as the thickness of oils of the same Cps rating may vary from different manufacturers! Stick to one brand for all your oils, so that you can reproduce the setup when its time to rebuild your diffs.