All of the catalog cuts I have seen express the GB stem extensions in inches, never in metric. And in my correspondence with those more knowledgeable across the pond I have been reminded of that when I've described a GB stem length as, say, 100mm. That's actually a 4" stem. I don't have my Holdsworth Aids catalogs handy, but memory is that the readily-available sizes were in half inch increments, from 2-1/2 to 5-1/2.
Dave Ross Portola Valley, CA USA
Jerry Moos wrote:
"Having a number of English frames to build up, I've been trying to
accumulate some old style GB stems. On a frame with a 55 cm top tube, I
typicall use an 80 mm extension, but I have not found a GB in that size,
although there seem to be plenty of 75 mm. This makes me suspect that
GB stem extensions were sized in inches, not mm. Is that the case? 3"
would be 76.2 mm, which one could easily measure as 75 mm. 4" would be
102.6 mm. If GB stems were sized in inches, were they available in
half inch increments, or only whole inches? 3 1/2" inches would be 88.9
mm, still a bit long for me on most frames, and I'm not even sure I've
seen a GB in that extension."