Abstract: An “all-in-one” spacer and seal useful in insulating glass units is based on silane-functional, organic polymer which preferably has a low permeability (e.g., curable polyisobutylene or curable butyl rubber) technology. This chemically crosslinking (curing) flexible thermoset spacer and seal offers a solution to overcome the current shortfalls of commercially available thermoplastic spacer materials. When used as an edge-seal in an Insulating Glass unit, the cured product of the composition performs the functions of sealing, bonding, spacing, and desiccating.