Where can I find my new ringtone on my iPhone?

I bought a new iPhone 3GS,and wanted to convert MP3 to ringtone.I have converted m4r format successfully by right steps.My phone have a ringtone icon which prove it to be converted.But it is strange that i can’t find something in phone ringtong setting.Any better iPhone RingTone Maker???Appreciate your early reply,i am so vexed about that.
Thanks in advance.