material:sponge block bonded with abrasive ,such as aluminum oxide ,silicon carbide. feature:flexible ,stretchy ,sponge block have different density . application: dry and wet grinding ,suitable for surface grinding ,and can be reusable .keeping long time grinding with water . different sizes :general size 100*70*25 ,125*100*25 ,140*114*5 ,125*100*10 and so on . grit: P36 P40 P50 P60 P80 P100 P120 P150 P180 P220 P240 P320 P400