As always for Tamiya - high precision mold quality and top quality throughout - I would expect no less, but these really do deliver!
Personally - I think it' better to run the plastic parts like this in the front of your car rather than go for the more expensive alloy upgrades. They are cheaper to replace, and are more likley to flex and take some of the force out of a serious accident. Alloy parts can bend - or even worse transfer the force to a more expensive part of your car!
I run these in my Tamiya TRF415MSXX, but they would fit a TB Evolution IV and TRF415MSX too, amongst other models.
I ordered 2 sets at a time just in-case and keep a spare in my pit-box. I live in the UK and thrse parts are either very difficult to get, or MUCH more expensive compared to RCMart.
A little tip - make sure you don't over tighten the kingpins when fitting these to ensure that you have smooth steering. It's a fine line between getting the kingpins in at a good depth into the part and going too tight, so real care must be taken.