I saw some of these buggers for about 5 bucks a set on subguns.com a few months ago and order 5 sets of them. Why? I have no idea, don't even own a glock right now. Anyway, the gentleman who sold them to me said they should only be used in 9mm glocks if I intended to actually use them underwater and that also I needed to seriously consider protecting my ears before I attempted it. I was expecting some really wicked and cool looking thing, it turns out that what I got was just some spring cups, look kind of like little washers or something. I was told you could still use the gun above water no problem, these just give the water somewhere to go. They're not illegal if I understand correctly, just not sold to the public due to litigation concerns. I think mine are up in the back of my closet somewhere. Again, I am just repeating some stuff I was told about them, I have NO first hand knowledge of these things, so please check it for yourself if you have some. Good shooting (and swimming I guess), Jake Salyards