Iron DiscOur Cast Iron Disc Pair 30 mm are available in ten different weights from 0. 5 to 20 kg. The hole in the centre of the disc has a diameter of 31. 5 mm. Material: Cast Iron They offer targeted muscle building and strength training, making it easy to create a routine that works for your goals. Whether you choose to combine them with other weights or use them individually, they'll help you enhance your fitness and sharpen your technique.