Molecular Sieve, Activated, Type 4A, 4-8 Mesh is a material containing extremely small holes of uniform size in order to block larger molecules while allowing certain smaller molecules to pass. They can be used in the chemistry laboratory for drying reaction starting materials and separating compounds. Ungraded products supplied by Spectrum are indicative of a grade suitable for general industrial use or research purposes and typically are not suitable for human consumption or therapeutic use.