Thanks for the replies, I don't have any vernier calipers/ or a way of measuring it accurately but I think it must be 25.4mm as it is far tighter than any other stem I've fitted. My worry is that I may stress the casting too much when I tighten it up on the bars, i've already scratched the bars fitting it.
Kona Explosif (in pieces)
93 Saracen Sahara Elite SE (in pieces)
Raleigh Ti Professional - winter duties
Raleigh Ti Track viewtopic.php?p=997725#997725
Voodoo D-Jab Ti project