Jumbo pistachios are large which is why they are called jumbo. It Looks almost like round but bigger hence some people call it big round. Kallehgouchi pistachio has a long history in cultivation as its been growing for more than 4000 years. Jumbo pistachios are available in the following sizes: 18-20, 20-22, 22-24, 24-26, and 26-28.