Yeah they are approx 15-20 km outside islamabad...and any F sector is good depending about your budget,,,starting from the lower like F6,F7,,,the lower the sector, the higher the prices,,,F6 is the most expensive among them,,,I mean VERY VERY expensive...F6 is expensive than F7, F7 is expensive than F8 etc etc..
You can buy a house in G sector,,its also a very decent sector close to F...
A 2 kanal house in F7 can be between 18-30 cror..
while in G7 it would be between 8-12 cror