Ray Bloc for Clothing is an advanced water-based formula with UV blockers scientifically formulated to protect the skin from harmful UVA and UVB rays by increasing the UPF rating of treated fabrics. Adds up to 30+ UPF to treated clothing. Protects skin from harmful UVA & UVB rays. Adds or improves the UPF rating of clothing Reduces UV transmission through clothing Enhanced with Aqua Armor Waterproofing NO odor, NO yellowing, NO stiffening Water based - NOT solvent based More information can be found at http://www.trek7.com/products/ray-bloc-for-clothing