Mezz insert material

[spliced]

Does anyone know what material mezz uses for its shaft inserts. It's a silver color, so not brass. Possibly aluminum? I'm going to be having a 5/16x14 mezz shaft converted to 3/8x10 with phenolic insert and I'm wondering how much weight change I can expect.

 

[HereWeGo]

I recently had this done to a WD700 and it went from 4.2 to 3.9 oz. I purposely called and ordered the heaviest one in stock expecting the loss.

 

[spliced]

Thank you!!!!!