The E27 smooth lamp holder in black thermoplastic material with switch allows you to to connect any E27 fitting lightbulb.
N.B. This lamp holder has a security system that, in order to protect you from electrical shocks while you are changing the light bulbs, does not allow it to unscrew.
If the necessity to unscrew it should present, it is possible to unblock it by pointing at the security flap you will find at the base of the lamp holder with a screwdriver, while you are turning the lamp holder.
Always ensure the electricity is switched off when dealing with the bulb holder.