I bought these hoping they would be a drop-in replacement for my HB NZ-4000 NT. Unfortunately they didn't fit, so I had to fill and redrill the holes. It was my first time attempting something like this so I just used tooth picks and super glue (the old holes are covered by the new tuners anyway). Was very pleased with the results.
These tuners are fantastic - my bass now has unbelievable tuning stability - I can play very heavily for many hours and it will still hold tune. The high gear ratio makes it painless to fine tune. They feel very, very solid.
All in all, would absolutely recommend them - just make sure to measure your existing tuners first!