“The science behind Hear Doggy!: Dogs can hear sounds at a higher frequency (0 to 45 KHz) than humans (0 to 20 KHz). Tuned to an ultrasonic range in the 24-28 KHz frequency, each Hear Doggy! squeaker is out of human hearing range, but still fun for your four-legged friend.
Hear Doggy! toys are available in 2 plush designs: Stuffed toys(Blowfish, Whale and Penguin, available in small or large) and Flats(Deer, Rabbit and Skunk) come in one standard size and contain no messy stuffing in the body.”
I purchased Kiara’s penguin from a local pet boutique (Just Dogs!) but apparently you can get them at Petco, Petsmart and amazon too!