Not to interrupt the SR Black fuse discussion but I sold my RED with 125 hours on it and am enjoying the beeswax immensely. The RED was not a good fit in the VAC preamp. in my situation....it was thin in comparison as I have a very revealing system. Maybe with 300 hours on it that would have magically changed but to late to know.
I just ordered an Audio Horizon fuse to try also and will use whatever works best with the back up after I am done with contenders. For everyone to endorse one fuse as the end all is simply wrong unless you have tried them all in your system.
As in everything audio YMMV.