These are the first (and, so far, only) parts to go on our hummers' most popular, old feeder.  I hated to buy a whole new feeder just because the bees had shredded these little plastic cages over the years, so I was thrilled to see them sold separately on Amazon.  I also find that little black spots, which I'm assuming to be mold, develop on these which I can't completely clean off, so now that I know where to get them, I can treat the birds to new ones every Spring.