<prompt> Engaging diameter of well flexed head in vertex presentation is -Suboccipito - bregmaticSuboccipito - frontalOccipito - frontalMento - vertical  <response>: Ans. is a i.e., Suboccipito - bregmatic DiametersMeasurement in cmAttitude of the headPresentationSuboccipito - bregmatic9?5 cmComplete flexionVertexSuboccipito - frontal10 cmIncomplete flexionVertexOccipito - frontal11?5 cmMarked deflexionVertexMento - vertical14 cmPartial extensionBrowSubmento - vertical11?5 cmIncomplete extensionFaceSubmento - bregmatic9?5 cmComplete extensionFace 