Unfortunately, I don't understand how it can be used since it doesn't have a hole for the air to escape. For me, it simply doesn't work

Attention.
Anyone who is about the same circumference as a toilet paper roll, meaning about 3 fingers wide, will have a lot of difficulty and will not enjoy it unless they have such a fetish; then it is cheaper to get a brick from construction to have the same feeling.

Nice to use, sleek design and high quality. Definitely worth it.

Haven’t had it for long enough to know so, but it seems like it’s going to last (For a masturbator that is).

Very good product. Tenga is by far the best masturbator for hand use. These specific models are very good and the design of the hole for suction play is very good. Now, for the black one specifically, it is the best in the series for me. It is quite tight so it constantly tries to push you out, but that's what makes it good. For example, the sleeve is so tight that you put it on your finger and it grips onto it. Of course, it has enough elasticity and will never be too tight. As for cleaning, I would say it is easy, classic with warm water, but drying takes days, the base is good for drying but because it is so tight and not transparent it takes a while to dry. Overall, very good, I definitely recommend it and it definitely needs lube like all.

It is the best thing I have ever bought. I personally had a great time with it. The annoying part is washing it. The feeling is perfect and it is very easy to use. It has a hole on the top that, if you want, you can close it with your hand and it feels like "suction", or you can use it without closing the hole. The sound is a bit strange but it doesn't bother me. I would recommend using this product for "help," or any other water-based recommendation: https://www.skroutz.gr/s/23165670/Megasol-USA-Eros-Aqua-Lipantiko-Gel-250ml.html. Finally, I would suggest not using the packet that comes inside the package because the ingredients it contains are not good for the "rocket." I will come back in a month to add further impressions. Also, you should pay attention to which one you will get because there is a difference between the white and the black. Silky White is more relaxed. When you insert yourself for the first time, you may even feel a little "Meh" until you start using the suction option and twisting the toy. Then you feel it! This is also better if your "member" is on the thicker side, as it is a bit more accommodating in the handle area.
Rocky Black feels more intense and much tighter. The internal ridges grip you tighter and giving it a twist or using the suction can make it feel overly stimulating! If you have a larger girth, it may feel too tight and be difficult to insert your "piece." I found that Rocky Black is excellent for when I just want to "finish." While Silky White is ideal for when I have more time and want to play and truly enjoy the sensations.

EDIT: 18/12/23
Well, I learned that for the best sensation, you should apply lubricant to the head of the "member," to the mouth of the Tenga Flex, and 2 drops inside the Tenga Flex, and then rotate it around to spread it everywhere, or you can do it with your finger, meaning to rub it around internally with your finger. I have been using it for a long time and I learned the hard way that it is not enough to just apply lubricant to the "member" because there is a chance of bleeding. I bled a lot because I was using it with a lot of force (I was in a rush at that moment, so I wanted to do it quickly).