GHS Strings BB40M Bright Bronze， 80/20 Copper-Zinc Alloy， Acoustic Guitar Strings， Medium (.013-.056)<div style="text-align: left;"><strong>[Product Information]</strong><ul><li><span class="a-list-item"> Model: BB40M </span></li><li><span class="a-list-item"> Featuring the air-tight Fresh Pack &amp; NitroPack singles， guaranteed fresh from the factory! </span></li><li><span class="a-list-item"> 80/20 Copper Zinc alloy on a Hex Core </span></li><li><span class="a-list-item"> Unique core-to-cover ratio. </span></li><li><span class="a-list-item"> Medium Gauge: 013-017-026-036-046-056 </span></li></ul></div><img src="http://ecx.images-amazon.com/images/I/51fWtxGM%2BVL.jpg" noproxy><img src="http://ecx.images-amazon.com/images/I/41sB47a4vOL.jpg" noproxy><img src="http://ecx.images-amazon.com/images/I/5139Yjw5LUL.jpg" noproxy>