Defendant argues that there were insufficient facts on the record to support the expert's opinion and that he needed to testify to the "specific imperfections" on the bullets compared. The court holds that the testimony was properly admitted. The requirement of questions used to elicit opinions being based on material facts in evidence is not applied strictly to expert opinion based on personal knowledge or observation. The court relies on Shawley in that the expert's evidence in that case was substantially the same and was found not to be prejudicial.