One of the most popular of the Garmin GPS units are the eTrex series. These GPS units are colorful with features that differentiate each unit. The base model eTrex, commonly nicknamed "eTrex Yellow", is Garmin's "budget" entry-level GPS unit. Other, more advanced eTrex models include the Summit, Venture, Legend, and Vista, each with various additional features such as WAAS, altimeter, digital compass, city database, and highway maps. Many models come in color and expandable-memory versions.[1]