The last time I went to CountryMax to get seed, I saw they had a bag of Sunflower Meaties. The bag looked like it had large unshelled sunflower pieces and some Black Oil Sunflower seeds. I had never tried these before as I usually buy Sunflower hearts, which are unshelled small pieces, and Black Oil Sunflower seeds separately. So I tried a 30 lb bag for $39. Turns out there were a bit more Black Oil seeds in the mix than I thought, and the birds, mostly Gold Finches, always eat the unshelled pieces first. The bottom of the feeder ends up totally black, filled with all the left over shelled Black Oil seeds. They eventually get to the shelled seeds and I had forgotten one of the reasons I switched to use less of the shelled seeds. One huge black mess under the feeder.
The hearts cost about the same, 40 lbs for $53, as the mix so in the end they are a better value. No shell mess and the finches really love the hearts. There are times I have about 25 finches at the feeders at the same time.