Check the listing for details. Stone Master Molds Rubber Mold for Concrete, River Rock 1-Step Corners with Plug. Color: Beige, Condition: New. Listed at 129.95 USD. Professional grade rubber mold that will last for hundreds of pours, created from natural stone to reproduce the natural stone's finest details, with matching River Rock flat molds also availableMade in the USA from plastisol rubber, including recycled plastisolNo release agent necessary, saving you money, time, and clean up, as well as easy, clean release of face color pigments, unlike plastic moldsEach of 3 available mold versions you purchase has one-of-a-kind stones with no repeats, with matching flat stone molds availableEach 1-step corner mold includes a specially designed corner plug for quick production Stone Master Mold's rubber stone molds in River Rock are ideal for making your own veneer stone for any indoor/outdoor project where stone cladding is needed. Our River Rock corner molds are designed to complement the matching River Rock flat stone molds. River Rock is a naturally river-worn, full-size stone. River Rock is most often used on log cabins and coastal homes, on the outside and inside. It is gorgeous on fireplaces, too. Our River Rock corners are up to 8 inches in diameter and vary in thickness from 1-2.5 inches at the center. Each mold makes approximately 1 linear foot with a grout joint. Stone Master's rubber molds are made from plastisol, which requires no release agent and will last for hundreds of pours. Each mold measures approximately 12" long by 12" wide, by 4.25" thick. This mold includes recycled plastisol. Made in the USA, both materials and labor. Available in 3 unique versions, with no stone repeats. Each 1-step corner mold includes a specially designed corner plug for quick production at no extra cost. 1-step corners allow you to pour the corners in one step: Pour the long, horizontal end first, place the plug on the mold, then fill the open, short end and lightly vibrate. Matching River Rock flat stone molds are also available.