Are fantastic if you don't really need to hear your girl say a word...
...if you ever watch TV and think a girl is much hotter on mute, this is wonderful. You can still hear all the grunting/moaning.
And its a very powerful thing (psychologically) for a girl to give up such an
important communication tool to another... And it can be a very powerful turn on.
And the blowjobs afterwards are great too.
Rik