The engaging diameters of the fetal skull depends on the degree of flexion present. Which is the longest diameter of fetal skull?

Mento-veical diameter is 14 cm which extends from the midpoint of the chin to the highest point on the sagittal suture. Must know: Submento-bregmatic diameter is 9.5 cm which extends from junction of floor of the mouth and neck to the centre of the bregma. Sub Occipito frontal diameter is 10 cm which extends from the nape of the neck to the anterior end of the anterior fontanelle or the centre of the sinciput. Occipito frontal diameter is 11.5 cm. It extends from the occipital eminence to the root of the nose (glabella). Ref: Textbook of Obstetrics by D C Dutta, 6th edition, Page 85.