Country Manor Wall Units Provincial Stone Curbstone Keystone Standard Units Compact Units Victorian Wall Stone Garden Wall Intermediate Units Corners & Caps Retaining Wall Accessories Celtik Wall Keystone Corners & Caps Photo Gallery | Product Colors | Specifications | Installation Guidelines The Keystone Retaining Wall is not complete without the "capping touch". Cap stones are available in 4" and 8" high units. Anchor Concrete Products provides a variety of face styles and either an angle back for curved walls or square back for straight walls. For more info on Keystone, Click here to visit the Keystone Website