Pre-Op and Intra Op markings all in one, can be used for smaller eyes. Bubble level for identifying the horizontal axis and has a knurled outer barrel for easy rotation without touching the marking blade. ASICO bubble level is more precise than a pendulum marker. Bubble sensitivity is less than 0.5 Degrees. Tabo System has markings of 0 and 180 Degrees at the handle and opposite the handle.