Neither, but it was actually 26mm. One had 26.38 and the other 26.6. I needed exactly 26mm for a 1" dowel to fit 28 holes and have enough room to squeeze out the glue. The holes these bits make are so big that I have to put self-tightening wedges into the ends of the dowels, and I'm lucky in doing this if I can get a perfect fit. Good luck to anyone who needs accurately sized holes.