So I have bought a cheap 26″rim to have my first go at wheel building, a wtb i19, and a cheap Shimano deore front hub. I have been using the rather good dtswiss wheel building site to work out my spoke  lengths but I cannot find anywhere that tells me what size nipples to use.

Do I go 12mm or 14mm oh wise STW wheel builders. (I am thinking 12mm??)

Ps. What size spoke key do I need too. Getting dt Swiss competition spokes and dt Swiss brass nipples, is a black 3.4 key what I need?

12mm is the most common, I would use 12mm unless you have a reason not to.

I use the DT Swiss spoke key

If you’re using the DTSwiss spoke calculator, you have to select the nipple length as the last step, it’s current default as far as I remember, is for 15mm Squorx (horrible things gummed up with threadlock that screws with your “feel”, in my opinion, of course), i’d usually replace it with 12mm unless it’s a special case requiring longer. A red Spokey Pro fits these nicely.

12mm, red Spokey.

Thanks everyone. 12mm and red spoke it is.

Don’t forget to alter your calculations to suit them.