Exactly what it says up there
I may need to replace a threaded headset and I can't remember what the 'stack height' refers too?
The total height of the headset, top and bottom cups etc, when placed on top of each other?
The height of the top part when in the frame - ie the bit thats left above the steerer tube to the top of the locknut thing? (hope that makes sense?)
The height of the total thing but not including the bits that sit in the frame/steerer tube?
I'm not sure what part to measure on mine and to look out for so as it'll fit the frame and forks ok?
Then one day you find, 10 years have got behind you ....