Read the label. It should list Oleoresin Capsicum (OC) as an ingredient. An alternative is the synthetic version known as CS (CS is banned in many countries). Also, it should state that the spray is the mist or fog type. Mist / fog canisters spray in a similar pattern as deodorant and thus allows coverage of a larger area. Remember that during an attack there may not be time to aim and there may be multiple attackers, which is why direct stream types of spray patterns are less suitable for self defense. Direct stream sprays like a water pistol and require careful aiming. It is better suited for law enforcement use where the officer controls the situation and has time to aim.
The size of the container is also important. Smaller is better for carrying with you as you can easily put it in your pocket or bag. Bigger is better for home protection. Consider fire-extinguisher size for home use.
