SHIMANO DURA ACE HEADSET HP-7410 1" Threaded Track Road Bike - JIS or

Shimano Dura Ace HP-7410 NJS-certified headset.For 1 inch threaded forks available in standard JIS or ITA size.Featuring lightweight aluminum construction, with wonderfully smooth cartridge sealed-bearings. Classic styling with modern functionality.
For deciding your size, you need to either check your current headset with a measuring tool suchas digital calipers/micrometer, or you can measure the internal diamter of your headtube of your frame, withdigital calipers, and also the fork bearing race section of your fork. 
If you head tube is closer to 30.2mm and fork closer to 26.4mm then please select the Italian size.If your head tube is closer to 30mm, and fork closer to 27mm, then please select the JIS size.
The HP-7410 is NJS-approved for use in pro keirin racing in Japan, but are also well suited to road bikes.
Stack height is 37.6mm including top and bottom head parts.
(Please note that the ITALIAN set is oddly marked by shimano as 'ENGLISH', so please do not be alarmed if you order an ITALIAN size headsetand the box you receive has 'ENGLISH' printed on the size. This is normal.)