KETO//OS NAT Raspberry Lemonade utilizes Pruvit’s most advanced ketone delivery system available. Did we happen to mention it tastes amazing in the Heart Tart flavor too?Produces the most bioavailable ketone salts through the first and only naturally fermented process. Now that’s Nutritionally Advanced Technology™.KETO//OS® NAT™Pruvit's Ketone Supplement produces the most bioavailable ketone salts through the first and only naturally fermented process. Now that’s Nutritionally Advanced Technology™.