A Totco ring just isn't a sub but is integrated in this article for usefulness. A little insert is positioned inside the drill string involving a pin and also a box connection. Here are some collar styles or shirt collar styles based upon 3 diverse types of collars in garments. https://typesofsubcollars45665.elbloglibre.com/27202696/little-known-facts-about-types-of-sub-collars