These self-heating patches provide comforting warmth for up to 12 hours to soothe menstrual cramps. Their ultra-slim design is discreet enough to wear under clothing - whether it's in the morning, before bedtime, or in the middle of the day.These self-heating patches provide comforting warmth for up to 12 hours to soothe menstrual cramps. Their ultra-slim design is discreet enough to wear under clothing - whether it's in the morning, before bedtime, or in the middle of the day.