The Corning® Elplasia® 12K Flask enables researchers to generate a high density of spheroids in a scaffold-free model. The Corning Elplasia 12K Flask contains 152 microcavities per cm², in a vessel footprint similar to that of a T-75 flask. Gravity, in conjunction with the Corning Ultra-Low Attachment (ULA) surface, and a rounded microcavity geometry enable formation of approximately 12,000 spheroids of similar shape and size. The ULA surface, a proprietary, animal-free, covalently bonded hydrogel, promotes the formation and easy harvesting of spheroids.