What wedfit means
A wedfit engagement ring is designed so that a straight, plain wedding band can sit flush against it with no gap. The setting is kept high enough above the band, or shaped narrowly enough beneath the stone, for the wedding band to slide right up against the engagement ring.
A non-wedfit ring has a setting that is wider or lower at the base, so a straight band will touch it only at one point and leave a small gap, or need a band that is shaped to fit.