Those are the diff cups that come with the new Magnum. CEN supposedly beefed them up a little. I have been wanting to try them just to see if they are any better, but I cannot find them online anywhere. Custom RC Cars said they have the in stock, but their website is way behind. Until I find them online, I will not be buying any. I may not even buy them then and instead spend my money on the swift buggy conversion. I would recommend you just do the diff cup mod and move on.