I have 4. They work great.
My wife knows I have and has seen me use it. She has used it on me.
These are not me.
You can control the amount of suction by loosening or tightening the cap on the opposite end of where your cock goes.
I have 4.
The original
Mouth
Pussy
& either the Ass or the STU type.
All have different nodules and patterns on the inside for different feelings.
Another good way to use them is to slide it between the mattresses or couch/chair and fuck it either standing up or kneeling. Holds it steady for you.
You can also put it in a tennis shoe which puts it at the right angle.
Two could fuck one from both ends if you remove the insert from the case.
Clean up is a snap and cornstarch brings the insert back to new quality.
They make a shower mount for them, but I don't have one.
Hope this helps !