The Numbuzin No. 6 Deep Sleep Mask Serum is generally well-received for its deep hydration, lightweight texture, and suitability for dry, dehydrated, or sensitive skin. Reviews highlight its ability to make skin feel supple and moisturized without being heavy or greasy, with many users enjoying it as a serum, overnight mask, or even a primer to improve makeup application. It is also praised for its fragrance-free formula and potential to calm skin, soothe inflammation, and improve overall texture without clogging pores.