These two metal balls were found in my friend's apartment, he has no idea what they are. If you shake them in a very specific way, they'll make deep resonating sound. :
Metal Ball,Metal Hemisphere,Steel Globe Factory - SHINY BALLS LTD
Solid Steel Balls - 30-809 [30-809] : Custom Iron Works, Best Stair Railings and Gate Parts on the Net!
THE MAKING(English Version) (314)The Making of Steel Balls - YouTube
Chrome Ball Realistic Isolated On White Background Stock Illustration - Download Image Now - Sphere, Metal, Metallic - iStock
Chrome metal ball realistic isolated on transparent background. Stock Vector | Adobe Stock