FGCI Patch Booster, 1 Quart for Resin and Gelcoat - 123811 Promotes Faster Cure, Harder Patch, Better Glosscoats Exterior Gel coats are Primarily for Contact Molding (spraying into a mold). 15 mils thickness or more is required and normally there is heavy orange peel along with tacky material on the inside surface. Spraying for repairs is generally done with a thinner film and needs to be smoother and cured on the inside surface. Patch booster is designed to modify exterior gel coat into a repair material, which sprays smoother, cures better in thin film, and has less halo at the edge of the spray. Converts exterior gelcoat into a material that sprays smoother, and cures in thin sections