5 lbs . Sterilized horse Manure Compost Mushroom Substrate Blocks in XL Bags. Composted following Penn State University instructions horse manure,straw, calcium carbonate, gypsum, exotic poultry compost. Then coir/peat. Gypsum & lime is added. new spectrum of vitamins, minerals. Amino acids added for Enhanced fungi. gypsum… ground up in shredder