I have a stihl 039 18" and a stihl MS 260 pro 20".
My wife has a stihl 025 16"
We only use pro chains (chains without the kick back links) they make it much easier to cut up stuff :P
Not sure if tractor supply, lowes, and home depot can sell the pro chains because of consumer safety issues, but you can get them for your saw at a lawn equipment store. I (like MEMRACING), also take my chains and have them sharpened. If you don't get the depth ,pitch and all that right, you are doing more damage than good. They only charge 7 bucks to sharpen a chain and it is as good as new!