They're pretty functional actually, if you are running a turbo at its limit and know what it's threshold is for safe rpms, these are way worth it. Spinning a FP green up to 165,000 rpms is fine, but if you get a massive boost leak and start hitting 180,000 rpms, the bearings in the turbo are gonna be sad!
One of the cars with the new fp red has one:
Their previous turbo was almost destroyed from over-revving.