Just come across this. I use a Hippus on my young mare. She is quite fussy in the mouth at present, some of which is I believe her 'stress' outlet. Her previous, good, owner tried many bits to find something she liked and had her in a copper wrapped single jointed snaffle prior to me buying her. In order to keep things as simple as possible at the start of her education I tried the Hippus as a precursor to potentially putting her in something with a port. She likes the Hippus so much I have left it in. There is no knobbly joint, it's replaced by a hinge arrangement which causes the bit to become a Mullen mouthpiece when it is still.