1.625is what they've been using longer than the C width.
This! I prefer it over the Jazz, my hand cramps if I play my MIA Jazz very long and it is why I bought a used MIM(fretless) Jazz which is in the shop to put a new Allparts(maple) fretted P neck on it. I love the necks on both of my Fender P-Basses(MIM & Am. Std.) but I wanted to have a Jazz that was comfortable to play.
I'll keep saying it until they listen, but the biggest thing Fender could do is offer the option of 1.50 or 1.625 on the Am. Std. basses as a reasonable cost option instead of only available thru the Custom Shop. It can't be that difficult to put a Jazz decal on a P neck(or vise-versa)!!!
