In the T-zone type 1, the squamocolumnar junction indicated by the arrow is fully visible on the ectocervix.

In the T-zone type 2, the squamocolumnar junction indicated by the arrow becomes only fully visible if the cervical os is open and the endocervix can be inspected.

In the T-zone type 3, the squamocolumnar junction indicated by the arrow is not visible and colposcopic examination cannot be used to diagnose or exclude CIN or cancer.