Hello there! Thanks your your great question! Honestly I do not know! I wish I did! But I bought these quite awhile back! But, with my diagnosis of MS I can no longer play around with jewelry making. That's why I'm selling it on here! It keeps me busy! Lol! Sorry I didn't have a straight answer 4 you! Take care! Oh, if it helps I haven't had anyone tell me they had any trouble! :-)