Pettit 6999 Sandless Primer is a pre-treatment primer designed to adhere tenaciously to unsanded fiberglass gelcoat. When properly topcoated with antifouling paint, the primer and antifouling paint will bond together, resulting in a finish with excellent overall adhesion. Use Sandless Primer over vinylester gelcoats, where sanding gelcoat may void osmotic blister warranties. It maybe used over conventional gelcoats as well, and as a tie coat between two part epoxy primers and antifouling paints.