cc41p It is waterproof and can be soaked in water for long time and can be utilized both in the humid and dry condition. The flexibility of the paper backing prolongs the life of the sand paper . Application: It is used for grinding and polishing the woodwork(wooden furniture and musical instruments),.metal and lacquer, etc. CC45P Features: It is waterproof and can be utilized both in the humid and dry condition. The paper backing is so flexible that the sand paper can be easily used manually and be suitable for polishing the curved surface of the workpiece.