The MA40 rim is based on the same extrusion used in the MA2. The only obvious variation between the two rims is their surface treatment. They may each be made of a different series of aluminum alloy, but we'll never know because the alloy composition is kept secret.
>The MA40 has their "CD" or "couche dure" treatment, what in the United States is called a hard anodized finish and is dark Grey in color. The anodizing on the MA40 is performed after it is hooped and drilled. All other aspects of the MA40 including the eyelets appear identical to the MA2 as explained above.
More specifics about the MA40 rims are available in the Rim table.