When choosing a cock and ball ring, there are several factors to consider:

1. Size: It's important to choose a ring that fits comfortably around your penis and testicles. Many rings are adjustable or come in multiple sizes to accommodate different users. It's generally recommended to start with a larger size and work your way down to a tighter fit.
2. Material: Cock and ball rings come in a variety of materials, including silicone, rubber, leather, and metal. Choose a material that is comfortable against your skin and easy to clean.
3. Style: There are many different styles of cock and ball rings, including single rings, double rings, and more complex designs that incorporate additional features like vibration or clitoral stimulation. Choose a style that matches your preferences and the level of stimulation you desire.
4. Safety: It's important to choose a ring that is safe to use and won't cause injury or discomfort. Look for rings that are made from body-safe materials, have a comfortable fit, and come with clear instructions on how to use them safely.
5. Price: Cock and ball rings are available at a range of price points. Consider how much you're willing to spend and look for a ring that provides good value for your money.

Remember, it's important to use cock and ball rings safely and in accordance with the manufacturer's instructions. Using a ring that is too tight or leaving it on for too long can cause tissue damage and other health issues. Additionally, anyone with a history of blood clotting disorders, cardiovascular disease, or other medical conditions should consult a doctor before using a cock ring.