Mapei Primer L Acrylic Latex Primer for Concrete (1 gal.) is a professional-grade, water-based primer formulated to promote superior adhesion on concrete and other porous substrates. Used prior to self-leveling underlayments, skimcoats, and patching compounds, Primer L helps ensure consistent curing and long-term performance. This easy-to-apply primer penetrates the substrate, reduces porosity, and minimizes pinholes and air bubbles in subsequent applications. Ideal for interior residential and commercial projects, Primer L helps create a stable, properly prepared surface for flooring installations including tile, stone, carpet, vinyl, and wood flooring.