Acme rod type?

1/4"-16 from mcmaster. Get the 3ft length and hacksaw it in half.

This is what I use: http://www.mcmaster.com/#93410a606/=sshscc

These are the nuts I got to go with it, if you need: http://www.mcmaster.com/#94815a007/=ssht8e

Thank you for the info. Ordered a new one.

This was very helpful info! Thanks! I can confirm this is what's needed if you want to extend the build volume of the gmax. I ordered up 2 - 3ft pieces and they work like a champ.

Glad the info was helpful. The link was for B7 steel which is more expensive, I've since switch over to plain steel which is half the price and works fine on the other printer I'm building.