BOSNY Polyurethane Expanding Foam B219 * Non Shrink * Fills Large Gap * Excellent Insulation * Seals Against Sound * High Yield Expansion * Multi-Purpose Foam BOSNY Expanding Foam is a polyurethane spray on expanding foam that dries fast and seals large gaps fast Dried foam can be sanding and shape painted on. Best for quick sealing of gapping holes in projects. A must in any project-based industry installation.