how do the cables connect together do they plug in or must they be wired together?

They plug in, the connector has 2 female receptacles

Can this be added to and existing connection without removing the RJ45's? ie can the RJ45 slip through this coupling?

No. Cable without a terminal is fed into part numbers 1, 2, 3 and then 4 (see diagram in product description). The RJ45 terminal is attached onto the end of the cable. Then the RJ45 is plugged into part #5. Do the same on the other side using the other end of the cable to be connected.

Questions & Answers: RJ45 Waterproof Connector IP67 Ethernet Network Cable Connector Double Head Outdoor LAN Coupler Adapter Female Cat5,8P8C,Waterproof RJ45 Coupler cat5 Coupler ethernet Coupler

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RJ45 Waterproof Connector IP67 Ethernet Network Cable Connector Double Head Outdoor LAN Coupler Adapter Female Cat5,8P8C,Waterproof RJ45 Coupler cat5 Coupler ethernet Coupler

Outdoor Waterproof Design: Toptekits double head Outdoor RJ45 LAN Connector Ethernet Network Cable Extension coupler Adapter waterproof Female to Female
Cable Extension Functionality: Used to connect two RJ45 cables together, Make two RJ45 cables work as one cable Straight through configuration, 8 Conductors with Gold-plated contacts
IP67 Waterproof Protection: Waterproofable when connected to IP68 when connected or capped, and won't rust. The waterproof connectors are sealed and ready to be installed into your case, controller, brief, tote, detonator, or anything else you might be installing it on
Harsh Environment Applications: Suitable for use in marine, warehouse, or any wet environment. It also has potting inside of it to prevent any water intrusion in case the cable breaks or someone forgets to put the seal-cap back on
Package Contents: 1* Waterproof RJ45 connectors included in the package
Durable Construction Materials: Made from PA66 nylon native environmental protection material with UV resistance, providing anti-aging properties and long service life
Wide Temperature Range: Operating temperature range from -40C to 105C, ensuring reliable performance in extreme weather conditions

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