I agree Dean. I was deep into reading about HF plasma grounding and just glanced at it and thought 1500 total length of screw -300mm in gantry legs gives 1200, minus more when he betters the design, so he could go away with that, cause anyways most people don't go faster than 10m/min in real life. And it was 1500mm travel , not screw length. I hope he did not order the screws. Anyways i will buy them from him if that mistake happened. its never a bad thing to have some extra ball screws.