This products are ideal for home gym strength training, toning your arms, improving body stabilization, and increasing range of motion. Material: Solid cast iron core, neoprene available in 2, 3, 5, 8, 10, 12, 15 lb. Features: Heavy-duty and durable cast iron core for long-lasting performance soft neoprene coating designed to protect your floor, reduce noise, and no rust issues anti-slip and sweat-resistant coating provides a secure grip during exercise anti-roll hex shape prevents rolling around color and number-coded for easy picking.