The present invention relates to methods and devices for insertion between adjacent vertebrae in a spine following removing at least a portion of a nucleus from within a disc. In one embodiment, the device comprises a member having a flexible wall surrounding an internal volume and a coupler that is secured to the flexible wall. The member is adapted to expand when filled with a first filler material to form an interior cavity. The coupler has a first access point, a second access point, a first coupler side hole, and an optional second coupler side hole. The first and second access points are adapted to removably receive one or more fill tubes. The fill tubes cooperate with the first and optional second coupler side holes to direct the first filler material into the internal volume and a second filler material into the interior cavity.