Hi Tony, don't know what the jet diameter is, but I do know that Base-camp have the No.3 jets in stock. Ian
0.60 to 0.63mm is about the nominal size for sure. I'll have a probe with my number/letter drills tonight to check. My 529 was a #72 (0.635mm) with a slightly worn orifice, but I can check my 3s as well Alec.
I reckon 0.6mm diameter jet aperture for a No.3 stove is correct. This link to a Radius No.36 I have said: “This Radius No 36 is jetted at 0.7mm, or 28 thou, which is bigger than my No 3 stove.” From: Radius No. 36 Stove * Best Regards, Kerophile.