Sanding Sponge Variety Pack includes four different grits: Fine, SuperFine, UltraFine, and MicroFine. Use on pre-fired or post-fired pieces. These sponges are flexible and will easily work around bends and curves. Cut sponges into smaller sections for use with different types of clay. Prolong use by removing metal remnants by lightly brushing with a toothbrush and remove clay powder remnants by rinsing in water.