COLOR. Classic Tortoise Shell MATERIALS. Cellulose Acetate DIM. 1.5'' Diameter Hypoallergenic Post - Stainless Steel Cellulose Acetate Material ~ Much stronger and more durable than an acrylic material. This material costs more than acrylic material to produce. Cellulose acetate is less brittle and wont break as easily. It is also a renewable resource ~ essentially made from a wood pulp. It is the same material used for high-end eyewear frames. This material will last longer and the quality is far superior!