Chassis accessory question

I bought an iStarUSA chassis (D416 for $110 on Newegg). Included in the bag o stuff like headers and screw included a few of these things in two sizes. I don’t know what they are and are looking for guesses.

I’m the middle is a header/screw for size reference.

The website also shows them in the product photo but doesn’t identify them

Update: I found that they are “expansion slot brackets”

Are these used to secure pci cards from wobbling back and forth?