Attention, the product does not create one ethernet port into two, but it takes two ports from the router and with one cable (the male one) transfers the ethernet wherever you want, and in the end you add another adapter like this and connect it to two devices. So instead of having two cables on the wall, you have one, you just add an adapter at the beginning and another identical one at the end. For multiple ethernet ports, you need something like this.
https://www.skroutz.gr/search?keyphrase=8-PORT+10%2F100%2F1000MBPS+DESKTOP+SWITCH
Anyway, the product works perfectly for its intended use

I use it in a local network with 20 users (in 2 terminals in areas with insufficient wiring) and they work flawlessly! The plastic for their fastening with screws needs attention during screwing because it easily cracks.

The product does what it was designed to do and does it correctly.

The previous 2 reviews contain a substantive error: this product does not create a second RJ-45 port, meaning it does not provide two separate and independent network ports originating from one. This is done by ethernet switches (which are active devices) and this is not an ethernet switch to multiply ethernet ports.

Attention: this product takes the 8 conductors of the ethernet wiring and divides them into 2 separate 4-pairs. Each RJ-45 female connector has only 4 wires available inside. It is designed to allow us to "pass" two separate 4-pair connections through one 8-pair ethernet cable. This product is always used in pairs, at both ends of the same cable. It cannot be combined with anything other than the same splitter. The two 4-pair connections it provides cannot carry network signals. If you are lucky, only one connection will be able to transmit ethernet signals, and only up to 100 Mbit (because 100 Mbit uses 4 out of the 8 pairs of the ethernet cable). The other connection is not expected to carry network signals.

The usual use of these splitters involves passing 2 independent 4-pair (usually telephone) connections through an 8-pair ethernet cable.