What are these weights?

[Kal130]

They make things you put them on heavier

 

[Brad_Blazer]

Sometimes they are useful in product testing for example hang them from a simply supported beam and measure deflection to test bending stiffness (flexural rigidity).

 

[Zxyrthe]

This board is a veritable fount of knowledge. Thanks for all the feedback. My brother bought them from a used fitness equipment store of all places. We'll probably use them for their pavement friction drag when they're not making things heavier.