Im building up a bike and buying pieces one by one. I have a 1" threadless headset and all the stems i've seen are 1 1/8". I was told i needed an extension? Can anyone help me out and if so where can i find an extension?

You actually need a 1 to 1 1/8 threadless adaptor, and almost any bike shop will either have one or be willing to get you one.

alright, thanks man