A kit for implanting a nuclear prosthesis, the kit comprising: a spinal implant device comprising: a flexible body defining: an outer fillable enclosure defining an outer chamber having a body aperture; and an inner fillable enclosure defining an inner chamber such that the outer fillable enclosure at least partially surrounds the inner fillable enclosure, the inner fillable enclosure having an opening in fluid communication with the inner chamber; a proximal plug configured to be coupled to the inner fillable enclosure such that the proximal plug controls fluid communication through the opening, the proximal plug defines a receptacle including a plug aperture and including a re-sealable membrane to control fluid communication through a proximal opening of the inner chamber, the receptacle configured to couple with a retaining element of an inflation stylet, wherein the plug aperture is positioned between the retaining element and the re-sealable membrane when the proximal plug is mated with the inflation stylet and is configured to enable fluid communication to the outer fillable enclosure; the inflation stylet configured to mate with the proximal plug and extend at least partially through the proximal plug, the inflation stylet comprising: a first lumen configured to deliver a fluid to and remove a fluid from the inner chamber; a second lumen at least partially surrounding the first lumen and configured to deliver a fluid to the outer chamber; and the retaining element configured to control insertion depth of the inflation stylet and to secure the inflation stylet to the proximal plug. a spinal implant device comprising: a flexible body defining: an outer fillable enclosure defining an outer chamber having a body aperture; and an inner fillable enclosure defining an inner chamber such that the outer fillable enclosure at least partially surrounds the inner fillable enclosure, the inner fillable enclosure having an opening in fluid communication with the inner chamber; a proximal plug configured to be coupled to the inner fillable enclosure such that the proximal plug controls fluid communication through the opening, the proximal plug defines a receptacle including a plug aperture and including a re-sealable membrane to control fluid communication through a proximal opening of the inner chamber, the receptacle configured to couple with a retaining element of an inflation stylet, wherein the plug aperture is positioned between the retaining element and the re-sealable membrane when the proximal plug is mated with the inflation stylet and is configured to enable fluid communication to the outer fillable enclosure; a flexible body defining: an outer fillable enclosure defining an outer chamber having a body aperture; and an inner fillable enclosure defining an inner chamber such that the outer fillable enclosure at least partially surrounds the inner fillable enclosure, the inner fillable enclosure having an opening in fluid communication with the inner chamber; an outer fillable enclosure defining an outer chamber having a body aperture; and an inner fillable enclosure defining an inner chamber such that the outer fillable enclosure at least partially surrounds the inner fillable enclosure, the inner fillable enclosure having an opening in fluid communication with the inner chamber; a proximal plug configured to be coupled to the inner fillable enclosure such that the proximal plug controls fluid communication through the opening, the proximal plug defines a receptacle including a plug aperture and including a re-sealable membrane to control fluid communication through a proximal opening of the inner chamber, the receptacle configured to couple with a retaining element of an inflation stylet, wherein the plug aperture is positioned between the retaining element and the re-sealable membrane when the proximal plug is mated with the inflation stylet and is configured to enable fluid communication to the outer fillable enclosure; the inflation stylet configured to mate with the proximal plug and extend at least partially through the proximal plug, the inflation stylet comprising: a first lumen configured to deliver a fluid to and remove a fluid from the inner chamber; a second lumen at least partially surrounding the first lumen and configured to deliver a fluid to the outer chamber; and the retaining element configured to control insertion depth of the inflation stylet and to secure the inflation stylet to the proximal plug. a first lumen configured to deliver a fluid to and remove a fluid from the inner chamber; a second lumen at least partially surrounding the first lumen and configured to deliver a fluid to the outer chamber; and the retaining element configured to control insertion depth of the inflation stylet and to secure the inflation stylet to the proximal plug.