This is Mr Hobby Mr Surfacer 500

Mr. Surfacer 500 should be on every modeller's workbench. Mr Surfacer 500 is the best for filling small holes, and imperfections, creating surface texture and filling gaps and is suitable for large-scale repairs and can be used as soluble putty. Can be diluted with either Mr Thinner or Mr Levelling Thinner. Can be applied in multiple layers as needed for that perfect finish.