Firstly and most importantly, the pickups themselves are simply AMAZING - fantastic tonal variety and no hum whatsoever in any position. I fitted them to my Gordon Smith SS which currently had the GS handwound P90s in it, so it was a direct swap in that sense. The originals were nice but they were very noisy (single coil hum) and it was an old guitar so all the pots were crackling and needed replacing as well. The Pickups fit the P90s spaces perfectly and all the pots fitted into the guitar, but be aware that the push/pull tone pots are quite large so might not fit a very slim guitar body. Now to the fitting: There are very limited instructions for what is a fairly complex soldering job (for me anyway) and I was very relieved when after many, many hours of soldering my friend and I had finished and found to our relief that everything worked OK. I know these are expensive but I would happily have paid another $50-100 for a kit that was better thought out and did not need soldering. As things stand my recommendation is to invest in these P90s because they are THE BEST - just amazing tones - but if you are a relative soldering novice like me, be prepared to either have a long, difficult and frustrating time fitting them yourself or (as I now wish I had done) to pay to get them professionally fitted by someone who knows what they are doing. But with all said an done - that tone is AMAZING and my Gordon Smith sounds even more fantastic than before and without a whisper of a hum or crackle.