Question about protection for steelbooks

[GoldenCobras]

Hello everyone!
I was looking to protect my Disney steel book/viva metal pack and was hoping someone can tell me if these bags are good.

I searched on Ebay

I asked the seller if they are acid free and they responded: This is acid free, BOPP plastic bag.

Size: 7.5" x 6" w/adhesive seal on flap to close (flap depth 1.5")

I read some threads here discussing rust on some steelbooks and also saw some talk about mylar bags. Any idea if the ones I posted would be ok or if there is a site that offers mylar bags which are the ideal size for steelbooks?

Thank you very much in advance!

***Edit*** I am sorry for posting an eBay link I must have looked over that in the rules, my bad. If you search "400 - 7.5 X 6 " BLU-RAY DVD CASE POLY SLEEVE BAGS JS84" those are the ones I am talking about.