There are many user who curious and ask for lighter shaft weight, so we try to provide shaft made from Aluminium. At the same time many user also ask for bigger shaft size especially for Japanese Setup GL, and we will provide size from 7mm to 12mm with 0.5mm increments.
We use the silver shaft design which have wider flange at the middle that can support the shaft better and improve stability. This feature is possible since we use bigger rod material, for more information about this feature please read Silver Shaft blog post.
Compare to Silver Shaft which use Stainless Steel material (density around 7.8), ALU shaft density is less than 3, so the ALU shaft weigh is less than half of Silver Shaft. But of course SS also much stronger compare to ALU. This ALU Shaft anodized in Gold and will became the default shaft for Golden Lever.