The product is a lot of 4 Pool Block PB80 Pumice Stones, designed specifically for in-ground pools. These pool cleaner stones are made of pumice, making them effective at removing algae, rust, and lime buildup from pool tiles and concrete surfaces. The Pool Block PB-80 model is known for its efficiency in maintaining pool cleanliness and ensuring a sparkling clean appearance for your pool or spa. Ideal for outdoor living and home maintenance, these pumice stones are a reliable and practical solution for keeping your pool in top condition.