Bostik Ultra Set Single Step Wood Floor Adhesive 4 Gallon 4 Gallon Size Bostiks Ultra-Set SingleStep is a one-part, trowel applied, tacking, moisture-cure urethane Adhesive, Moisture Vapor and Sound Reduction Membrane. This scientifically-formulated adhesive and membrane is very tenacious, has very low moisture permeability, and formulated with patent pending Thickness-Control Spacer Technology to ensure proper membrane thickness between hardwood flooring and substrate. Bostiks Ultra-Set SingleStep does NOT contain water, and has zero VOC as per SCAQMD 1168. Once cured, Ultra-Set SingleStep will create a tough, flexible, tenacious bond to a variety of substrates for gluedown installations of engineered, solid, and bamboo wood flooring while also forming an elastomeric, urethane membrane designed to reduce moisture vapor transmission from the subfloor; create a noise reduction barrier over the substrate; and establish an anti-fracture membrane which can bridge cracks that can occur in the substrate prior to or after installation (up to 1/8"). Ultra-Set SingleStep may be used over all properly prepared substrates common to hardwood flooring installations, including: concrete, plywood, particle or chip board (underlayment grade), well-bonded vinyl and ceramic tile, cement backer board, gypsum patch/underlayments (dry, above grade), cement patch/underlayments, radiant-heat flooring, and properly prepared terrazzo. Ultra-Set SingleStep may also be used to install plywood as described, as well as ceramic tile, marble, and stone inlays for light commercial and/or residential applications.