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look for a perfekt sized tube
Easier said than done. This is pretty close, but the bore may come up just shy of 1" depending on the tolerances. The 1⅜"×10g I used for my spacers should have been under 1⅛" bore based on the nominal dimensions, but fitted perfectly and I just had to turn down the OD to get the wall thickness right, so 1⅛"×16g may be worth a punt for 1" spacers. You could always hand ream it to size, as it's only going to be about 0.002" under if it's exactly the nominal size.
Of course, a proper tart would make the spacer taper so that it blended into the headset upper cover and the stem perfektly[sic] :-)
do thin spacers exist? I'm looking for 1" spacers for under a salsa ahead stem, maybe 10mm or so under and 5mm on top, but all my alu ones are too chunky and don't sit flush...