Solid lightweight rocks made from styrofoam and coated with Polyurethane plastic are made in standard and custom sizes. Styrofoam Core Polyurethane Rocks can be used in trade shows, theatre, school plays, movies, church productions and vacation bible schools along with various other uses. These rocks can also be used outside where you can not get real rocks at a location.  These rocks can also be made in any color.  No two rocks are alike.