No pins or mortar required, rear lip and interlocking joints secure each stone. Easy to install for experienced DIY landscapers. Natural stone texture. Creates nonessential wall and garden structures. Durable and environmentally friendly concrete is long-lasting and low maintenance. Color, dimension, weight and texture may slightly vary due to natural materials used during manufacturing. Lowe's 6-in H x 16-in L x 10-in D Grey/Char Concrete Retaining wall block in Gray | L16BWGC