OK to keep out squirrels but of no use for grackles and starlings. I have caged tube seeders for seeds and they prevent grackles and starlings but the space between the cage and the suet is not sufficient to keep grackles from sticking their heads through the cage. If the diameter were 2' larger all would be fine. As it is, if you have a starling and grackle problem, this is NOT your solution.

Grackle/Starling solution update: I used HEATHsuet cakes that come in a harder plastic wrap. I cut a circle through the plastic about 3" in diameter in the center of the front of the cake. Now the grackles cannot peck at the edges to devour the cake so they have given up. They cannot reach the center owing to the increased distance from the cage to the center. Only birds that's can fit through the cage can get at the cakes.

I purchased this a few months ago. The squirrels try but quickly give up. The woodpeckers love it. Even the Chickadees, Nuthatches and Goldfinches like it. And, we have some Pileated Woodpeckers that feed at it several times a day.

I don't have a squirrel problem with my suet feeders because I hang it from a pole they can't climb or jump to. I have a problem with grackles, starlings, and black birds eating all of the suet at one sitting. I tried a different feeder - one that the bird has to hang underneath to eat the suet but the big birds still managed to get some, and the feeder was very messy to open to replace the suet since the suet had been resting again the access door. When I got this feeder the big birds managed to eat just a little of the suet cake at the very corners and then couldn't reach it. Since then they haven't seemed to try anymore even when I put a new suet cake in. The small birds - Carolina wrens, chickadees, goldfinches, etc. and the various woodpeckers have no trouble eating it. The little birds hop inside the outer wire and eat. The woodpeckers hang on the outside and reach their beaks in to get the suet.

I have tried a few different styles of suet feeders in an attempt to attract flickers whilst discouraging starlings, and this one works best towards that objective. I hang it away from other branches so that there is no perch for the starlings to access it, but the flickers can cling to the side of the cage and poke their long beaks in to get the suet. Even if I hang it so that birds can perch on nearby branches while feeding from it, the starlings can only reach the suet which is on the very outermost corners of the cake.

The juncos and bushtits enjoy it, too.

I just read a few reviews reporting birds dying in this feeder after getting trapped in the 1" gap between the top of the suet basket and the lid -- you can see this gap in my photos -- so I am going to stuff some crumpled aluminum foil in that gap as suggested in order to prevent any casualities. Otherwise, a great design.

I have only just put out this feeder design, so don't have feedback on how well it works or how safe it actually is for the birds. However, after reading other comments about trapped birds I had an idea that others and the manufacturer may find useful. This item was intended to replace my old, rectangular cage feeders so I had a couple of them left. I used wire cutters to cut out sections and form hinged doors, then attached them to cover the open tops of the inside cage portions of the new feeder. The existing hinges work well on one side, and on the other side the wires could be gently bent back on themselves if not at too sharp an angle. The two tops folded over one another a little in this case, so hopefully that keeps them in place and keeps the feathered friends safe. Other than that, it does feel pretty solid and is easy to use so seems like a pretty good value.