I was looking for another 5K or higher concentrated gel caplet, and this one seems to have good packaging, good information, good website, and a trusted following. I also started using their basic multi-vitamin and am pleased with it as well. While there really isn't any way to actually measure the benefit of the product, I get a sense that it is reputable and of high quality. My long term measurement is to see if I make it through the winter season without a Cold or bug. So far, so good. Since I started taking higher concentrations of vitamin D in the winter months years ago, I have seen a definite benefit and rarely get more than a sniffle. A good immunity booster