What are those birth control things called that girls put in their arm?

I forgot what they are called but its a little tube that doctors put in a girls arm and it acts as birth control for 3-5 years.





What are they called and how effective are they?What are those birth control things called that girls put in their arm?
Norplant I think. They're just as affective as any other birth control which I think is about 99.9%