The implant for the female contraceptive called Implanon or Nexplanon is a small rod of about 4 cm long (40mm) and 2 mm in diameter.
This size is similar to that of a matchstick and the implant is soft, flexible and white or off-white.
A needle-like applicator made to fit this size is used to insert the implant into the sub dermal layer of the skin. It is administered with local anesthetic so you should only feel the pressure of the needle but no real pain when it is implanted.
The whole process shouldn't take more than three minutes, and you will only be left with a little bruising and mild discomfort for a few days after the implantation.
Nexplanon works by stopping ovulation even though some women still get their period irregularly with it. Your implant can stay in place for three years and then you should remove and replace it with a new one that is good for another three years.
I would still encourage you to use condoms though since Nexplanon only prevents pregnancy but does not stop you from getting sexually transmitted infections and diseases.
Here's a youtube video showing how Nexplanon (Implanon) is implanted where you can see the size of all the instruments used:
