Well… It can be both. When using the “push pump”, the core can pull out. But it can also unscrew when I simply put the “core cover” on. (Is that the right word?)
So, be gentle when you do any operation on the valve. And put some threadlock if you have any issue 
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My feedback on the TRENTASEI TPU inner tube.
I use it in my G36 with the braus carbon rim and KG ultimate tire at 3 bar pressure (I weigh 150 lbs).
I’ve seen no loss of pressure, no more and no less than with a butyl inner tube, and the valve obus has never come off unintentionally.
I’m on my 2nd puncture (1 on each tube). I’ve ridden about 1000km with the 2 TPU tubes, but the tire has a lot more. And I’ve had very few punctures before, but I think that with a butyl inner tube, I would have punctured the same way.
The repair is easy and seems resistant.
The first time, a small piece of glass was lodged in the tire, and more recently, there was nothing in the tire but it was cut.
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Still haven’t punctured my first tube, although I have ridden in broken glass a few times 
I’m wondering whether the NightRider tire could be a bit more resistant than the King George tire as it is a bit heavier.
Did you follow the procedure? Put the patch then let it rest for 8 hours before inflating it again? Or did you just do an usual repair + immediate inflating? Just wondering, if I ever puncture my tube 
Whether it’s a butyl or TPU tube, when I get a puncture I always change the tube, and do the repair later.
I don’t have any feedback on repairs since I haven’t ridden with a repaired inner tube. I’ve only been riding for a few days with the tube I repaired last November.
I shouldn’t have said it was resistant, it seems resistant and the patches are easy to stick.
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https://unicyclist.com/t/your-experience-with-tpu-tubes/279391/37?u=wheelou
Still no problems at all. But compared to many people here I don‘t ride a whole lot. And the muni sees less use since I bought a 29er for the daily trips on paved and gravel roads.
@www.einradshop.ch : any news from the TPU tubes testers? Do you plan to get more samples or a first batch?
The tubes are in production. There will be 20x 4.0, 24x4.0 and 36" tubes. Since I am also ordering tires, the delivery will not be by air but by sea freight. It will probably take around 3 - 4 months until I have the parts here. Now I hope that there will be even thicker 36" tires one day, the tube fits this 2.25" width, but it also fits up to at least 3".
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There was a problem with a 36" test tube: bubbles formed at the welding point and it lost air quickly. Unfortunately, the hoses have already been produced, but the manufacturer replied to me that the welding is not adjusted so precisely for the sample production. He promised me, however, that he would test several more tubes. I hope that the series does not have these problems. I can remember the Fatty tubes (sample). I had a problem with one of the tubes there too, but not with the series product. It is of course not a good feeling, but I trust the manufacturer, I have already had 600 tubes produced and 300 more are waiting to be shipped
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crossing fingers!
Small update on the 36" TPU tubes. Delivery is confirmed for the end of October. If there are no unexpected additional costs, the price will be CHF 29.90 / piece
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Great!
Now you need a partner in Europe to avoid taxes when shipping from Switzerland! 
Then the partner has to pay for it and they will include it in the margin. The end product will be more expensive :D.
Seriously: Normally customs duties/VAT are only charged above a certain amount, otherwise companies like Aliexpress and Temu would not even exist. I am sure that 1 tube falls below this threshold, maybe even 2. Everyone has to find out for themselves.
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