Viper II under-slab vapor barrier is the first line of defense against damaging water vapor and soil gas threats existing below the concrete slab. Viper II products are multi-layer (co-extruded), virgin polyolefin under-slab vapor barriers/retarders. The virgin resin used to manufacture Viper II contributes to its long-term stability and prevents the material from breaking down when used as a vapor barrier for concrete slabs.