D'Addario's Nexxus 360 Tuner offers fast, accurate tuning and is USB rechargeable!  Just plug the supplied USB cable into any USB power device and enjoy 24 hours of tuning time per charge.  It has a discreet, clip-on design with 360-degree rotation capability to provide the perfect viewing angle for every situation, and the super-bright, full-color LED display assures complete screen clarity in any lighting.