For those of you who do not know, you will start with the single sling and the biggest (lightest) ball. The ball has a free weight inside that will bounce around and jiggle as you go about your daily activities. The bouncing of the internal ball with cause your body to think something is falling out of your vagina, and make you unconsciously clench your pelvic floor muscles. You may experience some soreness if you are not used to exercising these muscles.
Once you are used to wearing the single 30g ball, you can use a single 40g ball in the single sling. After you get used to that, you can move up to the two ball sling and wear both of the 30g balls. I find that it takes some time to get used to, and you may wait months before going up in weights. When you feel like you have reached your full potential with the two 30g balls, move up to two 40g balls in the double sling. The additional weight will cause your muscles to clench harder, further strengthing your pelvic floor. Changing the balls from sling to sling is super easy due to the stretchiness of the slings.
If you feel that you have reached your maximum strength with The Kegel Trainer Set, you can do other exercises with them! For example, laying on your back and tugging on the retrieval cord while squeezing the weights is another fun, and pleasurable way to use this set!