Hi Quin Pro is a 4% hydroquinone whitening cream that comes in a 30-gram tube. This prescription-strength skin lightening product is formulated to help reduce the appearance of hyperpigmentation and uneven skin tone. As this is a prescription-strength skin lightening product containing hydroquinone, it should only be used under medical supervision. The active ingredient hydroquinone 4% works by reducing melanin production in the skin. Results typically appear gradually over several weeks of consistent use.