Smooth Fillable Onewheel Bonk

thingiverse

A hollow bonk that can be carried around as a lightweight object, and filled with pebbles or sand when needed to practice bonking. Can be printer in different sizes, or even distorted, as per your own preference. I would advice to glue a thin layer of rubber to the bottom, to keep it from sliding. Better print this in a strong material, e.g. PETG If you print this at 64% or 156% size, you get smaller and larger versions that fit inside each other (make sure to keep the rubbery layer thin), so you can take a couple of bonks with you at compact size and weight, start practicing with the smaller bonks and work your way up.