Menstrual synchrony by chance when there is menstrual cycle variability. Yang and Schank argued that when there is cycle variability (i.e., either women have irregular cycles, have cycles of different frequencies, or both), most women will have the opportunity to experience synchrony even though it is a result of cycle variability and not a result of a mechanism such as the exchange of pheromones. For example, consider two women A and B. Suppose A has menstrual cycles that are 28 days long and B has cycles that are 30 days long. Suppose further that when A and B become close friends, B
Menstrual cup find a larger cup uncomfortable. Length also needs to be considered: if a female's cervix sits particularly low, she may want to use a shorter cup. Capacity is important to women who have a heavier flow. The average menstrual cup holds around 20 ml. Some cups are designed to be larger and hold 37–42 ml. However, all cups currently available have a larger capacity than a regular tampon, which is 10–12 ml. A final consideration in selecting a menstrual cup is firmness or flexibility. Some companies offer a range of firmness levels in their cups. A firmer cup pops open