I think plastic is lighter than aluminum; I used light weight diff shafts, light weight outdrives, light weight 43 tooth spiral cut bevel gear and 3x15mm ti screws. Filled about 3/4 of the diff. with oil, and I believe it is the lightest diff. for the D8. no sence in paying $189 for each diff. made by Fioroni. Then again I've never tryed them. But still not paying $189 for each.