Bona Gap Master is a silicone free mastic designed to fill gaps between parquet blocks, around skirting boards and door thresholds. Based on polyurethane and acrylate, Gap Master can be sanded and overcoated with Bona lacquers. It contains no solvents, is odourless and can be used with all parquet finishes. It retains a high degree of flexibility. Expansion is approximately 7%.