If you are a bass guitar player then you definitely need a pick up device. A pickup device captures or senses mechanical vibrations from the bass and converts it to an electrical signal to produce musical sounds. But you have to find the pick up that best suit your needs. You have to consider the tone, the shape of the pickup hole to the bass guitar and one of the very important parameter of pickup design is the string width. The most common string widths are the 4, 5, 6 and 7 String Bass Pickups. Let' say you need a 6 string bass pickups you must know that the common width of the 6 string bass pickups are 82mm, 86mm, 92mm and 96mm total string width at the bridge. You can browse online to check out available bass pickups.