A:Answer We are happy to help you with your inquiry. The main difference between the OP101 and OP301 is the size. The OP101 is a 5 quart system and the OP301 is a 6.5 quart system. The other difference between them is the functions. The OP101 has 7 functions, Pressure, Steam, Slow Cook, Yogurt, Sear/Sauté, Air Crisp, and Bake/Roast. The OP301 has 7 functions, Pressure, Steam, Slow Cook, Sear/Sauté, Air Crisp, Bake/Roast, and Broil.