I recently found a ton of these jars with what i think might be specialty rivet, a quick google search didnt show anything similar though, anyone know what they might be?

no post, so not pop-rivets...no threads, so not rivnuts...   possible they were made to go into a given hole size and the "open" end turned down, but not sure.   

Material?
size? 

They look like ferrules that would be crimped on the ends of cord. They make them for stranded electrical wire but they aren't painted and they are shaped a little different.

They're about 1/4" long and 1/8" diameter some type of metal but they aren't magnetic

They look like electrical ground wire crimping sleeves to me.

Hello, All. Possibly referred to as a barrel crimp? Regards, Lou

What is inside those things? Could probably see better if out of the jars.

Identical in size and shape to  electrical ground wire crimp sleeves. Color is different.

They look like eyelets using in sewing and leatherwork:

Eyelets commonly come in a range of colors to fit the material being sewn.  They're like miniature grommets, but one piece, commonly used, for instance, where you need to reinforce a hole that something passes through.  If you still own a pair of dress-up shoes, look where the shoelaces pass through and see if they have eyelets.  Another place they commonly appear is where the string comes out of the hood on a hooded sweatshirt.

Hello, Bill. These may be sleeves for shelf pins. I have some at work, I will try to take a photo tomorrow. Regards, Lou