12 PCS Extra Large 4.15-5.30″ Smooth Natural River Rocks for Painting, Flat Painting Rocks & Craft Stones for Arts, DIY Projects & Creative Studios. EXTRA LARGE PAINTING ROCKS DESIGNED FOR COMPLEX ART: These generous 4.15-5.30″ painting rocks provide impressive stability and ample space for portraits, lettering, detailed illustrations, and layered acrylic techniques-letting your creativity expand without limits.