Jiffy makes these compressed discs using a 60/40 mixture of white sphagnum peat moss and treated coir pith. When dry, each pellet weights around 8 grams and measures 44 millimeters by 42 millimeters. Once you add water, the pellet expands into a full 1-3/4-inch diameter, 2-inch deep growing medium. Jiffy encases each disc in plastic netting to keep everything together.