The Gibson ES-335 is the world's first commercial semi-hollowbody electric guitar, sometimes known as semi-acoustic. Released by the Gibson Guitar Corporation as part of its ES (Electric Spanish) series in 1958, it is neither fully hollow nor fully solid; instead, a solid maple wood block runs through the center of its body. The side "wings" formed by the two "cutaways" into its upper bouts are hollow, and the top has two violin-style f-holes over the hollow chambers. Since its release, Gibson has released numerous variations of and other models based on the design of the ES-335.