Why are Sefiros called Midos:
The Sefiros are called Midos because they are measured. Each one of the Sefiros of Atzilus is measured in terms of how much Hamshacha it will receive of Chesed or of Gevura, and how much contraction it will need. The level in charge of measuring and forming the tailored Hamshcah to the Sefira is called Kav Hamida or the Zoharic language, Butzina Dekardunisa. Thius level is the level of Moichin Setima of Atik Yomin and is an aspect of Gevura.
 Torah Or Shemos 53a