River Stone Art Set Of 5 Large Metal Rocks Home Decor. A unique set of 5 large river stone like pieces, each slightly unique. These are heavy weight pieces, I would guess a silver tone brass. 4 are the same size and be is smaller. The pieces don’t stack on each other without the tray. A unique art piece, this may work outside as well. Comes with tray as well. Big ones are 9″ small one is 7″.