What is this called?

[bobster]

Hello all.
I have this antique chest of drawers with these little metal things I've never seen before. The drawers slide perfectly because of them. It seems like they should be called sliders but that's the name used for mechanical ball-bearing thingies. I'd love to get some more but can't find them, probably because I don't know what they're called. Any help?
Thanks a lot.