Limit of private parts from book “al-Kafi”

Muhammad Yaqub al-Kulayni in his famous “al-Kafi” (6/501) narrated that imam Abul Hasan said:

Awrat (private parts to be covered) are two; qabl (sexual organs) and dabr (anus), dabr is hidden by buttocks and as far as qabl is concerned when you cover qadeeb (penis) and bedatayn (testicles) you have covered your private parts. According to another narration, dabr (anus) is covered by buttocks and hide the front part with your hand.