Modern acupuncture needles are delicately polished stainless steel coated with silicon. They are extremely sharp and when inserted they can be entirely painless. Various techniques are used to enhance the effectiveness of treatment and some of these involve the stimulation of the needles. The sensations one feels with stimulation vary from a sense of heaviness or a dull ache to a feeling of electric flow. Most of these sensations arrive with stimulation and then dissipate. Once the needles are inserted and stimulated appropriately, patients well rest comfortably for 20-45 minutes. It is very common for patients to fall asleep during this restful period.