Decent material to weld for a change .
The casting has 2 cut outs to weaken it so it brakes in a controlled way in a rear end shunt .
It stops the drive shaft going in to the car .
These fail on modified track cars .
If it's in a kit car, they don't seem to support the nose of the diff properly, then the bushes either end of that support allow too much movement and . . .
I've fitted aluminium replacements to the one in the trials car - works so far . . . but then it's not actually down off the lift on it's wheels yet . .