A bass string is built in layers: a steel core, often an inner wrap, then an outer wrap. A full-thickness heavy string won't fit through most tuning post holes or bend tightly enough to wind, so the outer layers stop near the tuner end. That thinner section is what sits on the post.
That's why length matters. The full-thickness winding should end before the post, not on it. If the thick section sits in the post hole or over the nut, the string won't seat properly and tuning suffers. Choose the scale length that fits your bass rather than relying on trimming.
Taper wound strings narrow at the other end, where the string crosses the bridge saddle. That has practical benefits:
- A tighter-feeling low B on five-string and six-string basses
- Improved intonation on heavy strings
- More sustain because the string bends more freely over the saddle
S.I.T. makes taper wound sets including TNR45105L, TNR545125L and TNR630125L in Power Wound Nickel Bass, plus tapered singles from .100 up in Bass Guitar Singles.