RainGuard Blok-Lok Siloxane Water Repellent is an invisible clear penetrating water repellent for vertical surfaces. It is non-yellowing, low odor, zero VOC, and non-toxic. It is formulated to not be affected by weathering, salt, dirt, freezing temperatures, UV light, and wind-driven rain, among many other damaging elements. It dries down to a clear, invisible finish that does not change the surface texture or color. Ideal for use on vertical uncoated/unpainted, interior/exterior surfaces such as: concrete, CMU blocks, brick, wood, porous natural and artificial stone, masonry, and color integrated or unpainted stucco.