I think it is OK performance wise but no better than the MK3, however the construction of the MK4 with no circuit board with soldered connections, just wires pushed into slots in metal sheet looks cheap and nasty. The tool free connections for the incoming pair and extensions along with the wobbly clip on front plate don't seem too clever either. I didn't want one of these master sockets but I had a noisy line and the first thing the OR engineer did was change it to the MK4, didn't do anything for the noisy line fault of course, they are just replacing the older sockets.