Keystone是專為大專校院英語課程所編寫的英語教材，以 12 個日常生活常見主題為軸心，包括：休閒娛樂、電話英語、校園生活、文化交流等，發展出真實的對話語境和豐富的閱讀文本。各單元皆整理出重點字彙和文法，幫助學習者建立穩固的英語基礎，再透過聽、說、讀、寫不同面向的學習策略，有效培養全方位的英語技能。

Keystone offers theme-based learning materials and focused practice to enhance college students’ listening, speaking, reading and writing skills for major integrative proficiency tests. It also enhances students’ learning of target vocabulary and grammar points in each unit through spiral ordering which allows students to revisit the to-be-learned items in focused, meaningful contexts.