DuraBlock Stain Blocking Primer, 5 GalDuraBlock Stain Blocking Paint Primer is a multi surface interior and exterior water based bonding primer that uses bio based chemistry to replace toxic petrochemical ingredients without compromising quality. Use it to effectively prime surfaces that require a higher level of stain blocking, moisture blocking, rust inhibitor protection, and better overall bonding of the topcoat paint. The high solids formula with superior flexural strength enables