The one I received is plastic.
I believe they are standard.
Dear Valued Customer: Thank you for your question concerning Flapper Chain. The flapper chain will attach to flappers that use a looped chain. For additional questions on the Flapper Chain or any Fluidmaster product please contact us at your earliest convenience. Fluidmaster’s Technical Service Department is available Monday through Friday from 5:30 AM through 5:00 PM Pacific Standard Time. Contact options include: Chat www.fluidmaster.com/support E-Mail firstname.lastname@example.org and Toll Free 800-631-2011.
Hi Pete, this item is currently in stock online. The Homedepot.com will allow you to place the order for whatever quantity is available at the time in the online inventory. We appreciate your business and look forward to serving you in the future. Thank you for shopping Home Depot.