Acker-Stone 1-107-01-06-374-50-11000 Coastal 18" x 18" 6cm Coastal Mist Paver. Acker-Stone’s Coastal Series integrates mother of pearl shells with our innovative manufacturing techniques to produce an extraordinarily breathtaking and highly durable hardscape solution. Coastal features Acker-Lock, a patented 360 degree integral sealant. The grind finish provides a smooth, polished surface that exposes the shells and aggregates, leaving a one-of-a-kind look.