Consists of 6 capsules releasing levonorgestrel and is efficacious for 5 years. 24 hours after insertion, the plasma levels are 1-2 ng/ml, falling to 0.25-0.4 ng/ ml by 6 months (4-5 times higher initially). From then on they remain constant. If implanted on days 2-5 of the menstrual cycle, barrier methods are advised for 7 days. It can be implemented from 21 days post partum (using a barrier method for 7 days) and on days 1-5 after a termination. Progesterone levels become undetectable within 48 hours of removal of the capsules.