Horticultural grit also knowing as a potting grit. It is the ideal product to use with heavy clay base soils, you can mix it in to help with drianage. It is ideal to use for cacti or alpines, where drier conditions are more favourable. Using a neutral PH material is important as you can add it to any compost or soil withouth altering the existing PH of the material.  Due to this material beign a crushed granite it is popular for decorating rockeries, water features, haning baskets and ponds.