Proline Decorative Concrete Systems RS130 34"x 36" Random Sandstone Hammered Edge Stone Concrete Stamp. Our Random Sandstone Hammered Edge is one of our most popular patterns. This stamp comes in 3 versions (see Random Sandstone Groutable & Random Sandstone Wide Joint). Each stamp consists of 6 natural stones ranging in size from 9 Inch x 10.5 Inch to the larger 13 Inch x 19 Inch. As with all Proline patterns, this stamp comes in a thin-flex mat for finishing edges and against walls. This is a favorite among home owners, as it looks beautiful with any type of home design.