Two notes about replacement:
1) They don't fit _every_ single Sennheiser headphone that has the connector. My HD250-II's have the same connector, but because of that little stop block on the Clou Jaspis cable, they never got a solid connection, they never got past the ridge on the prong, so didn't hold, and was prone to intermittent outages and falling out. It would be nice if everyone with every type of Sennheiser headphone and a Clou Jaspis cable were to try it and report back, say in this thread. So far, we have, definitively: HD600 - yes, HD580 - yes, HD250-II - no.
2) The two prongs are not the same size, so make sure you are sticking the bigger one in the bigger hole.