I was given the Jopen Stella III kegal balls in return for my honest review by bonneamour. They are a UK based sex toy company that are relatively small. They stock a huge range of toys. You should check them out.
The Stella III Kegel set is made up from three graduated weights of kegel balls. This enables you to progress with the weights as you advance through your kegel exercises. The smallest balls weighs 20g this I recommend starting on if you are a beginner or new to kegeling. The medium ball weight 30g this can be combined with the smaller ball to make a total of 50g. The last and larger ball weight 45g this is the heaviest of the three and can be combined with the other two balls to create a total of 95g. The balls are coated in silicone with the weights stamped on a plastic circle on each one. They can be removed from the casing of the kegel system which is attached to the pull chord. You simply just pop the weight you don’t want to use out of the silicone casing. This design is great and I haven’t seen it on kegel balls before it enables you to customise your weights and advance without buying multiple sets of kegel balls.