It will be very tight! 41 mm is certainly still possible, but at 42 mm you would have to remove the foam adhesive tape (surface protection) that is attached on the inside. But the hooks are easy to bend, so something could certainly be done. I have bent two of them around our heated towel rail in the bathroom so that they hold well. Would be good if you could upload pictures with the scale...

Yes. 1 x item = 4 pieces

Come in a pack of 4

Four pieces.

According to research, these are also 4 pieces.

1 set a 5 hooks

According to research, suitable for door rebates from 2 to 4 cm.