There is a tricky sound hole on my guitar as the neck covering a bit the hole. Also I'm not sure that the hole is exactly 100 mm, since edges a bit rounded outside, so the actual hole maybe 1-3 mm less. Also the thickness of this sound hole cover is 12-13 mm, but the distance from body to strings on my guitar is approx 10 mm (yes, I like strings action as low as possible), so it is difficult to squeeze it in between. As mentioned in other reviews the rubber may leave some marks and it is extremely stiff. Otherwise, good enough if it fits your guitar.