— In an action to recover damages for personal injuries based on negligence and breach of warranty, the defendant appeals from an interlocutory judgment of the Supreme Court, Nassau County, dated May 27, 1971, in favor of plaintiff on the issue of liability. Judgment reversed on the law, and a new trial granted, with costs to abide the event. Reversible error was committed when plaintiff’s expert was permitted to assume a fact, not previously nor subsequently established, that the flask was nonhomogeneous and from it to *561infer what caused the flask to cleave. It is settled law that opinion evidence must be based on facts in the record and that an expert may not reach his conclusion by assuming material facts not supported by the evidence (Cassano v. Hagstrom, 5 N Y 2d 643, 646). Furthermore, to the extent that the witness sought to indicate that the flask in question was nonhomogeneous because the flask he examined was nonhomogeneous, his testimony was inadmissible because there was no proof that the flasks were the same (Graham, v. Board of Educ. of City of N. Y., 19 A D 2d 635; Cromer v. Gull Corp., 5 A D 2d 850; General Motors Acceptance Corp. v. Dunham, 242 App. Div. 307). In fact, the flask he examined was made several years after the one which cleaved. Rabin, P. J., Hopkins, Martuscello, Latham and Shapiro, JJ., concur.