I've been feeding our hummingbirds for about 25 years and this is by far, the best feeder on the market.  It holds a perfect amount of food to be easily mixed and consumed in a reasonable period of time without going sour.  It's durable (except when you drop it on a concrete floor as I recently did, thus this replacement).  Don't waste your money on plastic feeders.  Glass is cleaner and more sanitary and It doesn't trap bacteria or smells.  I hope Perky Pet doesn't decide to get rid of this model,,,,ever.