I use them on my 1982 Fender 57 RI and 1997 Fender 1962 RI P-basses, as well as my 2003 Fender 62 RI Jazz bass. They all fit in fine.
The 82 had Rotosound Jazz flats on it for the longest time, so I didn't need to adjust the truss rod much when I switched to them. Though I did need to loosen the truss a lot when I used Rotosound Trubass strings, and then tighten it again when I put the LaBellas back on a few months ago.
62 RI P bass didn't need an adjustment.
The jazz bass needed a tiny bit of truss rod tweaking.
I had some on my fretless P-bass and my old Jaguar and they sounded good on those basses. I was putting a whole new nut on the P-bass when I installed them and the Jaguar came with them on.
I remember when I switched on the strings on my main P-bass (from the Trubass) to the LaBellas. You could hear the wood creaking!
