"I'm a music teacher. I bought the 8-pak after reading reviews that some whistles didn't work. Of the eight, two were DOA, two others worked partially. Four were excellent. The whistle has four tone chambers that sound great when all are working. Construction seems hurried on some of the flutes rendering some chambers inoperable. Reminds me of buying Sax reeds... some are good some are bad. Even with the quality control issues - still a great price for the good ones. Definitely buy at least 25% more than you need to have enough."