This industry comprises establishments primarily engaged in manufacturing glass and/or glass products. Establishments in this industry may manufacture glass and/or glass products by melting silica sand or cullet, or purchasing glass. Cross-References. Establishments primarily engaged in-- ? Manufacturing glass wool (i.e., fiberglass) insulation products--are classified in Industry 32799, All Other Nonmetallic Mineral Product Manufacturing; ? Manufacturing optical lenses (except ophthalmic), such as magnifying, photographic, and projection lenses--are classified in Industry 33331, Commercial and Service Industry Machinery Manufacturing; ? Grinding ophthalmic (i.e., eyeglass) lenses for the trade--are classified in Industry 33911, Medical Equipment and Supplies Manufacturing; and ? Manufacturing fiber optic cable from purchased fiber optic strand--are classified in Industry 33592, Communication and Energy Wire and Cable Manufacturing.