Today’s invention is a set of physically large kettlebell-shaped shells made of stretchy foam rubber.
These are designed to have a slit in the top so that even a large kettlebell can be placed inside. The shells have no external markings.
The shells are all the same size and may accommodate conventional kettle bells of any weight, so that people aren’t
a) tempted to show off with weights that are too heavy or
b) embarrassed by using very small weights when beginning exercise.