Feeling in the use of the product: 1.product material: The head is metal, and the shell and tail cover are high-quality plastic. 2.Treatment principle of Electronic Acupuncture Pen is used electrical pulses to to stimulate acupuncture points then to activate cell and dredging the channel, while there is a condition to generate the electrical pulse, that is, current's positive and negative poles must be turned on. The pen is a monopole current(the nib) output, so the other pole current should be conducted by hands and form circumfluence with the nid of the Electronic Acupuncture Pen, so that it will produce electrical pulses. So it is normal to feel a little numbness and shock of the holding hand, like "Electric leakage, Electric numbness, Electrical Stimulation" of Electronic Acupuncture Pen" is how the meridian pen works, not quality problem. The solution is: use the whole hand to hold the end of the meridian pen tightly, so the feeling will be much weaker, and some will not feel the electric numbness. If you can't stand the numbness at all, stop using it. (The work of the Meridian Pen requires a 1.5V AA battery. The voltage that the human body can withstand is 36V, please use it with confidence.) Note: 1.It is not recommended for people with a pacemaker. If you need to use it, please test it from level 1 on a normal body part. Can be used after acupuncture test. If you can't accept the stimulation, please stop using it. I wish you health and happiness. 2.During hot weather, part of the gel may evaporate. Please do not worry. The role of the gel is to relieve the irritation of the machine and skin contact, no special effect. You can use your home massage cream, lotion, aloe vera cream, etc. instead of gel, the same effect. Package Includes: 1 x Meridian Energy Pen(1 x Spheroidal Type Head is on the pen) 1 x Dome Type Head 1 x Manual 2 x Gel 5 x dental floss pick (3 purple,2 yellow) (gift for you)