At first glance this looks like a normal loose ring with a lozenge. It is a correctional or schooling bit that locks at certain angle thus becoming a straight bar. When a horse is working well the bit will lie comfortably in the mouth, but when the horses opposes the riders hand then the locking system comes into play.
This bit has now been renamed by Sprenger to the Max Control
Available in 12.5, 13.5 and 14.5.
New for 2019 is a slimmer version of this mouthpiece -12mm.