This all black Tee-Connector made by PCE Austria.
Designed to fit to products like outdoor lights, so each light has a 16A pluh, plug a 16A socket so the user can daisy chain extra lights. The bottom of the Tee is a cable gland, for wiring to your product
A very neat and simple answer to many wiring problems by featuring a plug and socket in one.
The PCE version are quick and easy to fit.
IP44 240v 16A 2 pin + Earth