The BDOCRSP2 2.5L Roof Seal Primer is a Bond It brand, one-part, solvent-free primer designed to prepare bitumen surfaces and roofing felt for the application of liquid roof seal membranes. It acts as a bleed blocker, preventing bitumen from staining through the top coat and enhancing the bond strength of the waterproofing system. It is applied with a brush or roller and is suitable for external use.