Proline Decorative Concrete Systems 3RS 36" x 36" Small Seamless Roman Slate Concrete Stamp. Prolines Roman Slate is now the standard in the industry. Copied by many, but none can hold a candle to this original favorite. Proline uses a special formula in its manufacturing - making the stamps lighter in weight yet more durable. Our seamless textures, with the exception of touch up size, come with handles for easier application. Proline was the innovator of the seamless texture skins, make to overlap each other for a simple application. Roman Slate is a great pattern for any area-inside and out.