Front derailleurs have gotten a lot better over the years, but even with the newest groupsets, quick downshifts at the base of a climb can throw a chain off the inner ring. This chain catcher weighs very little and stops your chain from dropping, slowing you down, and potentially scratching your frame. Installation involves loosening and reinstalling the bolt holding your front derailleur, so be prepared to reset the derailleur height and angle.
Compared to the Shimano equivalent master link, this is about a third the cost. The manufacturer of this product says it can be re-used 5 times. Shimano says their master link can't be re-used at all. So, if all you care about is cost, then this master link is the way to go. I've used this master link for about 500 miles and I can't tell the difference between it and the Shimano equivalent. Of course even a single failure would negate any cost savings. Only time will tell.
Bought on sale for a climbing century. I was concerned I would not be able to use it with my Shimano 9150 DI2 since it was not recommended. I run a sub-compact (50/34). It worked in all gears but didn't want to risk going big-big gear option. So I set my DI2 to full syncro mode and limited gear options to drop down the front to 34 when gearing down (higher up on the cassette) on the rear cassette from 27. This avoided the big-big gear selection that put a lot of stress on my rear derailer. Worked great!
I switched out my old Ultegra crankset to GRX (FC-6800) as I wanted lower gearing. As I learned that the GRX chainline is slightly different and it would be difficult to keep the old Ultegra FD (FD-6800) from rubbing I also changed out the FD to this GRX810. It's important to find and download the Shimano installation and adjustment instructions as they don't come with the components any longer. Anyway, they made if very easy to install and to adjust to prevent rubbing at all chain angles.
The GRX FD-RX810 seems very much like the 105 FD-R7000 on my new road bike. It shifts quite nicely - smooth and easy. After 26K miles the old Ultegra FD was pretty beat up and ready to be replaced anyway.
