Distance and, in general, extremeness.
Spartan Stadion 5K / 20 OBSTACLES
Spartan Sprint 5K / 20 OBSTACLES
Spartan Super 10K / 25 OBSTACLES
Spartan Beast Half Marathon / 30 OBSTACLES
Spartan Ultra 50K / 60 OBSTACLES
Spartan Trail: 10K & Half-Marathon / NO OBSTACLES
Hurricane Heat is 4 hrs hard group workout
HH12HR is 12 hrs hard group workout
HH24HR is 24 hrs hard group workout
The Agoge is minimum 60 hrs extreme race
Spartan KIDS Race is for 4 to 14,9 years old kids.