Lol, yeah, I was a little confused... You can buy the jump rings already made at theringlord.com in any color and metal you want, as well as size. Aluminum would work for this, though, and if it's not the cheapest, it's very close. Seriously... around three dollars for about five hundred or whatever... it's a lot when you're doing something like this. You can make several markers this way. Now, ID is inner diameter and it's typically in inches, I believe. They cater to use silly people in the USA, who don't conform to the rest of the world lol... even though they're Canadian (ringlord is). I suggest the saw cut ones over the others, so you don't have that pinch on one side. Also, if you buy enough over time (it just keeps accruing) you get a free gift card to buy free stuff with! It's not a whole lot but hey, it's better than nothing! I've found them to give me exactly what I wanted for the price I saw, shipped in the time mentioned, etc. I've never had a problem with them. Also, they keep track of all your orders, even when they're already sent to you, etc. You can always look things up in your account to see past stuff you've bought. You can use past orders to order again (if you want to order the same thing again) set up a wish list, make different lists of stuff to save on the site where you can easily choose one, then check-out and order.
Oh, they also have riveted rings, which are jump rings that have a hinge on the side opposite from the opening... that way, you don't have to worry about opening them wrong. Normal jump rings, you have to open them so they look like a spiral- you have to pass the ends by each other, basically. If you don't, you warp the ring and it pretty much becomes useless and ugly. :s