304 stainless steel ball solid small steel ball-3 mm : Amazon.co.uk: Automotive
6/8/10 mm steel ball, metal ball, round steel ball, solid steel ball-10mm : Amazon.co.uk: Business, Industry & Science
Solid Metal ball, a bit larger than a baseball. Not perfectly round, rough finish, tiny bit of rust. Found it while walking my dog (near Birmingham, AL - if that's helpful). :
THE MAKING(English Version) (314)The Making of Steel Balls - YouTube