TANGE LEVIN 34mm stack height excellent quality traditional looking headset with low stack height Ideal for use on older British frames – now also have in JIS dimensions which will fit most older British frames with no modifications. The low 34mm stack height will suit frames fitted with older British headsets which normally have a similar stack height. 

I can supply either a Tange Levin headset with 26.4mm crown race diameter and inset race diameter of 30.2mm (Campag 1in) or with 27.0mm crown race diameter and inset race diameter of 30.0mm (JIS and older British)

Please indicate in the notes whether you want a headset with 26.4mm crown race (Campagnolo standard) or 27.0mm crown race (JIS & old British standard). A cheap vernier calliper will help determine what you need if you do not know. 

Fork Crown Race Seat Diameter and Head tube Insert Race Diameter 

For 1in headsets Campagnolo settled on a standard crown race seat diameter of 26.4mm with an insert race diameter of 30.2mm. Japan with the JIS standard settled upon 27.0mm crown race seat diameter with an insert race diameter of 30.0mm which was virtually identical to that used for the most part in the UK prior to about 1975 unless a Campag headset was fitted. However most steel frames from the last thirty years use the Campagnolo standard and even the Japanese manufacturers mostly made headsets to the Campag dimensions. 

An important consideration with choosing a headset is to ensure that your new headset has a stack height the same or less than your current headset. Before removing the headset measure from the bottom of the fork crown race to the the top of the lower head race where it fits into the head tube. Secondly measure the height from the lowest part of the top frame race to the top of the lock nut. Add the two dimensions you have measured together and that is the stack height of your current headset.Your new headset must not have a stack larger than the old one.
For a frame without a fitted headset measure the length of the head tube (A). Then measure the length of the fork steeer tube from the base of the crown race seat to the top the column (B). Subtract A from B and that is the maximum stack height headset you can use – you can use a headset with a smaller stack height.