Dear Customer, I understand where you are coming from and sorry for the confusion. We have different frame suppliers and they have different measuring methods, so we re-measure the frame size and upload it to the website. Therefore, you could rely on the measurement listed on the frame page. As checked, this frame FBOM1782
has a size of 53-18-145(Medium). We understand that choosing a perfect frame size online can be tough sometimes so we suggest that you could please check this link https://www.firmoo.com/help-p-1.shtml
for reference. I hope this is helpful. Have a nice day!