Like Routledge's offer of downloadable audio to the "Colloquial..." courses, Tuttle's offer is best if you already have the relevant book or set of flashcards (e.g. Tagalog for Beginners, Continuing Korean - Textbook, Chinese Flash Cards Kit Volume 1) but didn't get the accompanying CD. Unlike Routledge, Tuttle hasn't yet jacked up the prices of its printed media, and so you might be able to find a cheap used copy of some book by Tuttle (quite a lot of Tuttle's language-learning material (even current editions) nowadays goes for $15 USD, give or take, on Amazon Marketplace) and not worry if it's missing its CD since you can just download the required audio files from the website.