Grit Question!

[werttyy]

What is the proper shape for grit? like these? : http://cherrystonegrit.com/grit_sizes.html, http://www.chicken-house.co.uk/acatalog/Mixed_Poultry_Grit.html#a489, http://www.chicken-house.co.uk/acatalog/Crushed_Oyster_shell_for_poultry.html#a487 because i have been looking around for circular stones to feed as grit. since i didn't want ragged or jagged pieces hurting their throats. Do flat pieces work? Are they supposed to be like that? Can they actually swallow it?! Please help! (After all, every chicken eats grit, and we all have chickens right?)

 

[Yay Chicks!]

How old are your birds?
I use the Cherrystone grit...I believe it's the #2 for my year old chickens. When they were little I used Chick grit.
The second link you posted came up as oyster shell, which is not used for grit but as a calcium supplement.