The Novistone dry-stacked polymer cornerstones are usually used for retaining walls. Smoked grey stones harmonize with all siding types. They are resistant to expansion, contraction, cracks as well as discoloration caused by ultraviolet rays. They also resist wind and impacts. Being maintenance-free, it is a lightweight, easy and quick to install the material. This corner is 5 3/4-in x 15 5/8-in in size and comes in a box of 5 units. It is certified testing by independent laboratories and comes with a limited lifetime warranty.