Only then ... Hui Ugh !!!

My wife and I are building a house in timber framework construction.
All electrical outlets and light switches are set by us, and must by 12 mm chipboard V100 and 12.5 mm gypsum fibreboard (Fermacell).
Because of previous recessions, we decided for the Wolfcraft hole saw.
The delivery of the article was done as usual damn fast (that explains the first star).
The first 5 holes went very well, the hole saw came well through the material and the ejector was working fine (2nd star).
Then abruptly denied the ejector and we had rausprokeln the discs with the screwdriver. Much worse, however, that the focus clearly subsided, so that the hole saw after a total of 25 holes was no longer usable.

Conclusion: For smaller renovation work well suited if the building project gets bigger I would choose another product.