A:Answer Hi there, and thanks for reaching out to us about this trim kit! We regret any confusion over whether this kit will fit model PEB9159, and know this may have caused inconvenience. The number you listed, JX9159SJ2SS, does not appear to have an exact match in our system. However, the trim kit you asked this question on, JX9152SJSS, is indeed a fit for your model. The 12.3" figure refers specifically to the frame opening. Since the microwave fits inside the trim kit for a built in look, the height of the microwave and the trim kit opening may not be an exact match - the trim kit frame will cover a small amount of the microwave's face once it's in place, hence the discrepancy. The overall maximum height of the whole trim kit is 19 1/8", so it is large enough for the microwave. We hope this helps clear things up, but if you have any other questions or concerns we're always happy to help, here or over social media. All the best! -Sarah@GEA