Re:
I use similar on some of my bike, they work well.
In fact if I ever use Syncros stems then I use them, everything is rigid and aligned, which help the angled top caps out.
Star it's can be out of alignment are are easy to bend.
Much better in Alu steerers too, so I use 1" in 1-1/8".
Just check the dimensions of each bit.
If you search their site you'll find the same thing but PlanetX and currently more expensive. It is the top part that needs to sit snug in the steerer
Both say you need to choose the Silver version for MTB forks, yet there is no choice. The fatty version is separate.
I would send them an email and ask them what the ID range is for it.
Have a look at alternatives on CRC and their reviews. I know BrandX do some.