Why is it a different size in the top and bottom? I have no idea. Maybe you do.
Planet X sold me this for a frame they 'manufactured'. Obviously they didn't know why either, because it didn't fit.
Bit that goes in the top of the head tube measures 44.17mm.
Bit that goes in the bottom of the head tube measures 49.75mm.
If someone fancies offering the correct headset size name for this kind of snake-oil, it might well be appreciated.
(£10 collected from Brockley, SE4.)