Zyex by D'Addario Zyex Bass Strings use a composite synthetic Zyex core that provides gut-like rich and complex tone combined with power and clarity for both pizzicato and bowing. Pitch stability is excellent after minimal break-in time. Zyex bass strings were developed primarily to offer outstanding pizzicato attacks and sustain as well as superb bowing response. Get the sound and feel of gut strings with more evenness, projection and stability than real gut. Zyex is a new generation of synthetic material creating strings that are extremely stable under drastic climatic conditions. All strings are composite synthetic core with the windings listed