
My wife and I have tried about every brand of those, so here is my "review"(using her user feedback also). I'll discuss their use afterwords.
Shiney black "Extreme Fetish: hideously floppy

(doesn't line up with chin), unduly large diameter for something that short(her input)

. Slippery and uncomfortable to the wearer. Velro adjustments tend to snag hair of both wearer and recipient


.
Adam & Eve w/small glass dido:all lines up nicely with your face, etc., but a glass dildo is a little on the hard side for the rocking motion that ultimately occurs when preforming oral sex with one of these on

. The straps feel a bit rough against the thighs(her input)

. Plus: Has snap opening for using dildos that has a suction cup type base

.
"Accomodator": The cheapest made, but still the go-to one. Cons: made of latex, will stretch out and need to be replaced after 50-75 vigorous uses as the outer "skin" will start to slide around and bind up on the inner dildo, creating a pinching problem. Pros - dildo can be removed and replaced with many others, this is the cheapest in it's class, fits the head and chin nicely.

:biggrin1:
Personally, I would like "The Accomodator" style/build, but made out of silicone with maybe some kind of fiber embedded in the silicone so it doesn't stretch too far.
Why use? Like some said, hand gets pretty uncomfortable getting down there whilst one is performing oral sex. Feels good apparently:redface: - it fulfills an fantasy/consideration of having intercourse whilst having oral sex performed on one(female). I(guy) like feeling my partner(wife) enjoying an incredibly good orgasm

- leaves her wanting to have more sex, rather than finishing her for the evening. They are goofy looking - don't model it with the lights on. Just let her look at it, dim the lights and then put it on. Suggestion1: start some conventional oral, get things nicely wet, then pause for the 3-8 seconds it takes to put it on....if you are tummy down you can keep it below you to warm it up a bit. SUggestion2: get used to the difference in the two straps' (unadjustable) length: if you get the shorter, neck strap on your hand first, you will have no problem getting this on quickly in the dark.