I use these in my guitars and have not experienced any problems. Make sure to squeeze out ALL the excess moisture so the sponge is DAMP...not wet, and be sure to dry it off outside completely especially between the flaps that hold it in the sound hole. It's my understanding that it DOESN'T work well with all finished (such as the ones with nitro finishes), but with gloss finishes on two different brand guitars, I've never experienced a problem.

I also understand that the hard plastic ring is there only for shipping purposes (so says my luthier) so be sure to remove it before use so you don't scratch your guitar.

Taylor's web site says to allow humidifiers to dry out before re-wetting or you can over-humidify the wood. Since this is a sound hole humidifier which humidifies the inside of the guitar, you might want to supplement with another type of humidifier near the headstock to humidify the fretboard.

I have one of these for my Martin, my Taylor and my hand made classical. It is very simple to use if you use it correctly.

First, take the dumb plastic ring off and throw it away. When you fill it, make sure you squeeze out ALL of the excess water and use a towel to dry the outside and the space in between the two side wings that will touch the soundhole. Only insert one of the wings on a dread sized guitar. If you buy the small one for a classical, both sides fit easily.

I live in Central PA and I refresh the sponge about once each week in the winter. On very cold and dry weeks, I will also put a Planet Waves small instrument humidifier by the headstock to keep the neck properly humidified.

The advantage of the Kyser is that you can use tap water. The Planet Waves requires distilled water.

I have never had condensation buildup nor damage to the top. It installs very easily. My luthier recommended it and now some of my friends have switched over to the Kyser as well.

It would get a 5 star rating if they ditched the dumb plastic ring.

This is the worst humidifier I have used. It can severely your instrument. Stay away. Get a real humidifier for your quality instrument. Buy this if you have a guitar that cost around $89; that is, if you feel the guitar is worth caring for.

My acoustic guitars took a beating this past winter with low humidity; there was fret buzz galore! I placed one of these spongy-type packs in the soundhole and a week later, NO fret buzz. My guitars played perfect ever since. I'll be using these every winter, faithfully. Only drawback is the soaking sponge- you gotta really shake the water out before applying. Use an old towel for that!

Yes, this is a great humidifier at a reasonable price; and yes, the plastic ring is horrible.

The ring might be intended to make a tighter seal, but it only served to make it more difficult to put in and take out of the soundhole. Furthermore, in the process, I put a ding in the edge of my beautiful taylor 810. (@#$^%#$@!)

No mention of the ring in the instructions and no good reason to keep it, so ditch the ring asap.

I have the skb clip-on type and the planet waves between-the-strings type, but I like the kyser soundhole type the best. I have about 4 of them now.

I couldn't fit it in the soundhole of my baby taylor, however, so I use a different type for it.