HYDRA SPONGES are the best polyester sponges on the market. They are Hydraphiliated - an extra manufacturing process that gives these sponges tremendous water holding capacity, more than any other polyester sponge! Contractors and home owners a like will appreciate the best grout clean up sponge on the market, the Hydra Sponge.The HYDRA SPONGE is the preferred washing sponge by professionals. They are more durable than any other polyester sponge and more cost saving than any natural sponge. They wash out clean, dry soft, and are always uniform in size and quality.