In a 1995 interview, Randy Bachman indicated that he thought that using the word "fragile" as a title for a rock album, as Yes had done with their 1971 album Fragile, was "strange." He thought that BTO music could be "dropped and kicked" without breaking, so, without intending any commentary about Yes, the band "tongue-in-cheek" called their next album Not Fragile.
The album marks the debut of guitarist Blair Thornton, who, unlike his predecessor Tim Bachman, is billed on the album liner notes as "second lead guitar". Blair's dual-guitar solos with Randy Bachman are prominent features on many Not Fragile tracks. It proved to be the group's most popular album (not counting compilations), and is the only BTO album to have reached #1 on the US Pop Album charts. "Roll On Down the Highway" and "You Ain't Seen Nothing Yet" were hit singles, with the latter hitting #1 on the singles charts in November 1974. Other cuts had significant airplay on FM rock radio.