OP; Saw your comment: "He said he had to make a headset press because his wasn't long enough, which surprises me because 270mm isn't that long."

- Most of the off the shelf headset presses would be unable to squish your headset in due to inadequate length. I think there is just one brand that offers an extension piece, but it may not be the brand your builder already has and the price for the piece is a series bite...
- One can just make another entire tool for about $15 which seems to be what your guy did. PM me for pictures of a XXL long one if desired [. Mine will easily handle 375mm headtubes, but I had to mod it yesterday to support installation of the "FSA Pig" 1.125 inch threadless headset as it has a huge lower cup to support 1/4" bearing balls. The original tool's lower plate was a huge washer (made for a 3/4" machine bolt) that just fell into the middle of the Pig's lower cup so the modification made out of a piece of 1/8" plate steel became necessary. The plate ($4.75) was found in the decking materials section at the home store and already had a hole in it, requiring just a few file strokes to open it up enough to fit the diameter of the threaded rod I had started with. Did the job very well.

Hope that helps
/K