The Ernie Ball Soundhole Cover suppresses unwanted noise and feedback, maximizing the output of your acoustic or acoustic-electric guitars. The soundhole cover is designed to fit in most acoustic soundholes, while the durable rubber material is soft and will not damage your guitar’s surface. Protect your guitar from that undesired screech and hum while eliminating dirt and debris inside your guitar with the easy-to-install, no tools required acoustic soundhole cover from Ernie Ball! Intended for full size acoustic guitars with 4” sound hole diameter. Does NOT work on guitars where the neck protrudes into the sound hole. Tapered shape from 3.98" to 4.064”.