Standard Days Method® (SDM) is a simple fertility awareness-based method of family planning based on a woman's menstrual cycle. Appropriate for women who usually have menstrual cycles between 26 and 32 days long, the method identifies days 8 though 19 as the fertile days. To prevent pregnancy, the couple avoids unprotected sex on the fertile days. SDM has a 95% efficacy rate when used correctly. A woman can use CycleBeads®, a color-coded string of beads, to help track the days of her menstrual cycle and see which days she is most likelyto get pregnant.