The 5.7×28mm cartridge is designed like a small rifle cartridge; the casing has a small neck to accommodate the projectile, which is a 31 grain bullet. In its original configuration, the bullet has a steel core for penetrating soft body armor. The projectile design was modified to FMJ in order to be sold on the commercial market.
This cartridge is fed through detachable box magazines.
- SS90 Type I - Original version of the round featuring a steel-cored projectile that measures 23.26mm.
- SS90 Type II - Redesign of the SS90 with an aluminum-cored projectile measuring 24.10mm
- SS190 - Replacing the SS90 in 1993, the SS190 uses a shorter projectile, allowing it to be used in pistols such as the FN Five-seveN. A version of the P90 using this round was introduced alongside it.
- L191 - Tracer round.
- SB193 - Subsonic round. Formerly designated SS193
- SS192 - Civilian-use hollow point round introduced alongside the IOM version of the Five-seveN pistol. It was discontinued the same year that it was introduced.
- SS195LF - Civilian-use hollow round with lead-free primer
- SS196SR - Civilian-use sporting round using the Hornady V-Max projectile
- T194 - Training round
- SS197SR - Civilian-use sporting round using the Hornady V-Max projectile. Manufactured by Fiocchi under contract for FN Herstal, and has a muzzle velocity that is 30 m/s higher.
- SS198LF - Uses the same lead-free projectile and primer as the SS195LF, but propels it at roughly a 30-m/s (100 ft/s) higher muzzle velocity. It has a green painted tip, and its sale is currently restricted by FN to military and law enforcement customers.