These products are ideal for home gym strength training, toning your arms, improving body stabilization, and increasing your range of motion. The material is solid cast iron core, Neoprene. Heavy-duty and durable cast iron core for long-lasting performance soft neoprene coating designed to protect your floor, reduce noise, and have 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.