Not possible to lose screws
These items are self clinching fasteners made for thin sheets.
The screw is a part of a nut and it is not possible to lose it.
It can be with or without spring in order to the nut could go to the wanted position.
You can use them for example in steel covers of machines.
You can choose from PF11 (aluminium), PFC2 (steinless steel), PF30 a PF31.
More information you can find on the page 13: