These are direct replacements for the kit parts in a TB Evolution IV and TRF415 MSX/MSXX. They will also fit the MR editions. They are much stronger than the lightweight blue alloy drive shafts and the build quality, as always with Tamiya is top quality.
I run these in the front of my car, although I know that some people also run them in the rear of their cars too for extra strength. These are ideally suited for usage in the front as they can take an impact better than the blue alloy drive shafts.
Take care when you re-build your drive shafts - a good little tip is to put a small amount of grease in the drive cup and on the end of the drive shaft. Be careful not to put too much - just a small wipe over will do. If you put too much grease on, it can attract dirt and grit, which can wear the components quicker. I use Tamiya AW grease in the drive cup, and Tamiya CeraGrease HG everwhere else, and this seems to give very good performance.