I got these to try out and eventually settled with them in my QiYi 6x6 (The original, not the V2 or X-man) because it had the stiffest springs out of all my cubic puzzles to the point of being sorta tiring on the hands after a while. After swapping them in and carefully tensioning, it became much easier to turn and since I could tighten them more without stiffening it like it's original springs, became more stable. Very nice!

The only thing I would have to say is that these springs change the Yuxin Red 6x6 immediately. Right after swapping them (which took forever because I basically tore apart the whole cube and internals), the Yuxin Red turned a ton faster and it actually felt so smooth it felt soft. One of the only things that is bad about these springs is that, believe it or not, they are very similar to the Yuxin Red's springs. Don't be alarmed though, what I mean is height wise, both springs perform very differently. If you use the method I used, be sure to use some lube or tape to help hold the pieces together. Though I would recommend Kevin Hays' method to changing the springs on his video called: "How to properly setup your Yuxin 6x6 (and thoughts on sponsorship bias)".
Link: https://www.youtube.com/watch?v=UqRtr-zPaP8
He goes over some things like a simpler method to changing the springs, what tensions work well for it, and the types of lubes that works well for the Yuxin Red.
Overall these springs may be a little similar to the Yuxin Red's (which may cause confusion), but if your careful you won't have this problem. If you purchase or plan on purchasing a Yuxin Red 6x6, be sure to spend one extra dollar to improve speed and performance on the Yuxin Red. If you buy the springs and put them in a Yuxin Red you will definitely be pleased with the outcome.

These are essential if you are getting a yuxin 6x6. After doing the swap, it felt sooooooooooo much better.

I used this on my Yuxin 6x6 like everyone and it improves it a lot!!!

First I will say I loath spring swaps. I nearly destroyed my shengshou 6x6 and 7x7 with spring swaps and I swore never again. The hype about these in a yuxin 6x6 made be cave, and I decided to try them out. I can say without a doubt these springs sent the yuxin over the top. I use to have pops all the time now I never get pops. The inner layers now move easily with one finger on edge pairing. These have made me a believer that spring swaps actually work! If you have a yuxin 6x6 you must get these.

If you put these in your Yuxin 6x6, it will be 10x better. Popping is nonexistent. Locking stops pretty much completely. If you buy these (or take them from your Yuxin 5x5) and this will compete a lot with the AoShi.

After replacing the yuxin 6x6 springs with these, it became SO MUCH BETTER!!!!!!