I'm from Italy and here in Europe we don't use that type of foam so I could be wrong, but after searching the internet for various Volare datasheets I think that the number 2 (or 4 or 6) refers to the density of the material.
I found this description about the density of the product on a data sheet:
VOLARA is available in many styles and thicknesses. The most common are 2A, 2AF, 4A and 6A. The EO grades are suited to medical and food applications, but typically require large minimums. Generally VOLARA densities go up as thickness goes down: 2# density (2A and 2AF) is common in 1/8" thickness, 4# density (4A) in 1/16th and 6# density (6A) in 1/32" thicknesses.
I hope this is helpful
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Simone Morbin
Conservator
Freelance/Private Practice/Self-employed/Independent
Belluno
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