No. The pelvic ball is a unique oval sphere which is easy to insert into the vagina and works through vibration. Kegel balls or ben wa balls, on the other hand, are designed so that their spheres work based on volume and weight rather than vibrations.
As the volume of the balls decreases, the weight increases. Physiotherapists who specialize in the pelvic floor indicate that the most important factor in a pelvic floor exerciser is not the size or weight but the vibrations produced.
Discomfort can be normal at first, as you are not used to exercising that area. Discomfort may also be due to using the vaginal sphere for too long or doing activities that require exertion (you can walk or move around the house using it but not lift or exercise with it).