Which bean bag is the heaviest? A set of 20 bean bags where size and mass are NOT as you may think! Children cannot automatically assume that the biggest bean bags are the heaviest. Bags are of mass 30, 60, 90 and 120gms and 13cm, 16cm, 19cm and 22cm in size - but all mixed up! Children will need to use their senses to vary the system of classification! Colours may vary.