When we tried to pull out the air around the roller, the glass mat was also shifted together and it was hard to use. Since another thing of the size bought at the same time moves without problems, I think that it is product unevenness.
I think that the best point of choice is hardness (hardness), it is just good hardness. Although it may be a bit harder, I will not defeat the strength of pushing, I will turn it tightly. I will continue to buy it. In the future, I would like to arrange each size.