Jon,
I have 2 La Marzocco Strada baskets. 21g and 17g. The 21g is measured 58.6mm, the 17g is measured 58.9mm diameter.
The VST are 22g & 18g. Although my baskets don't say VST on them, they are to my limited knowledge manufactured the same way or by the same company. There is the bar code, the basket serial number, and the grams dosage marked on them, there is the document with the actual holes size distribution graph, and the photo of the holes just like VST. It is also mentioned in the attached document that the imagining is VST. There is the theoretical access to that rumored database. The price is identical $29.00.
You see I am careful not to say that these are VST baskets manufactured 1g smaller to LM specifications for their Strada machine - because I don't have the proof, knowledge or confirmation of that.
Their diameter is not identical as you can see above.
Do I know what is the actual diameter of VST? Nope. I see the post above that someone said 58.7mm. So now we have 3 different diameter sizes.
I double checked on VST website and there is no mention of the diameter of the baskets. The only reference to diameter is the recommendation to use tamper size 58.3 or 58.4mm.
I don't know if there is a difference between LM Strada and direct VST tolerances. I sent an email to VST this last Friday and did not receive a response yet.
Thus far, it look like the old advice still valid: Get your basket and see what diameter it is. We have posters here who said that there is a difference for them between the tampers sized 58.0 and 58.3 or .4 - Their tamper gets too tight, and some of their friends prefer the 58.0mm.
All of the above is leading me to believe that the diameter of the VST or Strada baskets is not made to precision.
Since you have much more experience than I have in this area, I would like to know your thoughts of the above?
Thanks,
Dan