What part of a fuse's construction and materials give the fuse its amperage rating? Is the fuse element larger or smaller in relation to its ampacity, or is there some other material/variable in play? Also, what causes a fuse to fail faster or more slowly? I am using Hifi Tuning fuses in Maggie 3.6R speakers that call for a 2.5amp fuse for the tweeter and a 5 amp for the midrange. The Magnepan manual lists the stock fuses as normal blow, and they caution against using slow blow. All HiFi Tuning fuses only come in slow or fast blow. My question is, would slightly exceeding the recommended ratings offer more conductivity in the way of larger fuse elements? And would using slow blow vs fast blow offer any more conductivity, safety aside? Forgive me if my thinking about fuses is too simplistic, as I just don't know how they actually differ in order to do what they do. I just wonder if pushing the envelope a bit would offer even more current across this part of the path. Thanks to all for your advice.