Obligato Series Violin E String 4/4 Size Steel Medium Loop End. Obligato E string for violin. Core made of new synthetic fiber, available in a variety of calibrations with loop or ball end options. Warm, rich and sonorous tone quality, very rich in nuances. Impressive amount of volume, very dynamic response and great playability. This series features excellent uniformity across all strings, a flexible feel under the finger, and is resistant to changes in temperature and humidity.