The prong-set gem will fit any internally threaded Industrial Strength brand body jewelry.
The three prong titanium setting is available in ten colors and the cat's eye gem is available in six colors.
The 18g/16g prong-set gem will fit 18 gauge and 16 gauge jewelry and the 14g/12g will fit both 14 gauge and 12 gauge jewelry.
This threaded end will fit Industrial Strength brand internally threaded jewelry, but may not fit your other brand jewelry if purchased elsewhere (due to possible differences in threading). The gauge of the end must be the same gauge as the jewelry it threads into.