Injected as a single component, catalyzed AV-248 Flexseal is a moisture activated MDI-based polyurethane resin. The chemical reaction is catalyzed by using AV-249 Flexseal AC and uses moisture as an initiator. Like other hydrophobics, AV-248 Flexseal withstands wet/dry cycles and reacts with moisture; but unlike other hydrophobics, it forms a resilient, impermeable flexible foam. This high quality resin is designed for sealing active and potential water leaks in various cracks, and annular spaces where flexibility is needed but is susceptible to wet/dry cycles. Avanti’s AV-248 is one of the most versatile products on the market.