Selecting the Correct RJ45 Connector

Selecting the Correct RJ45 Connector

Written by Don Schultz, trueCABLE Technical Manager, Fluke Networks Copper/Fiber CCTT, BICSI INST1, INSTC, INSTF Certified

All Ethernet cable must be terminated. One way is to use a RJ45 Ethernet connector. For some great background on the most effective terminations to use during your installation (and why) see Choosing the Right Termination - Keystone Jack vs RJ45 Connector vs Field Termination Plug. As it turns out, RJ45 8P8C connectors are not the best choice for solid copper Ethernet cable, although there are situations where using them is not avoidable. Given that you may need to use this style of termination due to installation constraints, it behooves you to fully understand how to pick the right one!

tipsThe correct terminology is 8P8C (eight position, eight contact) modular plug. Often 8P8C plugs are referred to as “RJ45” and we will continue to use that term for simplicity.

Selecting the correct 8P8C (aka RJ45) connector for your Ethernet data cable is entirely dependent upon the type and construction of the cable to be run. Technically, Category has nothing to do with it. It is all about fitment. Information is half the battle in the quest for success, and this can be a bit tricky. Let’s get fitted!

I am including a video with this blog to provide some hands-on examples in addition to the written portion. Both bring something to the table, and the video should be watched in conjunction with reading.

Do I need a shielded connector?

This is an easy one. If the cable is shielded, you will want to use shielded RJ45 connectors. Conversely, if the cable is unshielded, then use unshielded RJ45 connectors. Using a shielded connector on an unshielded cable will yield no benefit, assuming the fitment is correct to begin with (and likely it won’t be). Shielded connectors are typically “up size” in nature, and usually won’t make proper electrical connections with thinner unshielded Ethernet cable conductors. Another item of note is using shielded RJ45 connectors on unshielded Ethernet cable is bad form as it may mislead someone into thinking the cable is also shielded.

When it comes to unshielded connectors on shielded cable, don’t do it. Shielded cables need shielded connectors for the cable shield to function properly (the outside of the metal connector functions as an extension of the cable shield and is used to bond to ground).

Shielded vs unshielded


Once you have decided on whether the RJ45 connector (also referred to as a plug) should be shielded or not, the next thing is…

Research for the right cable & plug

Any reputable manufacturer will have detailed specifications and publish them. Avoid any manufacturer that does not publish all of the required details as you will be playing a guessing game from the start. They are likely not a manufacturer, but simply a reseller that will offer little to no support for their products.

Do not shop by Category for the best RJ45 connector, as this can be misleading when mixing components from different vendors! “Category” stated on any bag of RJ45 plugs can be misleading when it comes to proper fitment, period. There is little, if any, correlation between the two. Are you, the consumer, being lied to? Not precisely. When a manufacturer (that only makes plugs and not the cable, for example) states a category on their plug it’s because they assume the consumer is not technically savvy enough to choose based upon technical data. This is not only a bit insulting, it is confusing. A properly documented and advertised plug would be listed as “Unshielded RJ45 Plug, 3 prong for solid copper Ethernet cable, fits up to 7.00mm OD and 0.94 to 1.04mm insulated conductors.” So, what did the “XYZ Manufacturer” do? They advertised their plug as “Cat6”, leaving out all the important stuff, and this leaves you guessing.

trueCABLE is the exception here since we sell a system. We go the extra mile of testing our components together. So, a trueCABLE CatX unshielded RJ45 plug will fit and function on all of our unshielded CatX Ethernet (we will note exceptions as necessary). We also thoroughly document our connecting hardware so you can make an informed choice if you are not using trueCABLE brand Ethernet cable.

So what if you are dealing with brand “X” of one thing and brand “Y” of another?

For the Ethernet cable you will need to know:

  • OD (outside diameter) of the Ethernet cable (the overall thickness). This is often expressed in millimeters (mm).
  • Conductor insulation diameter (the actual conductor wire plus insulation thickness) and likewise this measurement is often expressed in millimeters
  • If the cable has solid or stranded conductors
  • Copper AWG gauge
For the best RJ45 connector you will need to know:
  • Cable jacket OD that the plug is capable of accepting
  • Conductor insulation diameter range that the plug is capable of accepting
  • If the plug is 2 prong or 3 prong. 3 prong plugs will work with stranded and solid copper conductors. 2 prong plugs work with stranded copper only.
  • Copper AWG gauge
tipsPro tip: Be aware of the potential tolerances (-/+) for the conductor insulation diameter of the Ethernet cable. Try and pick a RJ45 plug where the middle of the plug fitment range matches the stated nominal diameter of the insulated conductors of the cable you intend to use. This will help to account for any manufacturing tolerance differences that can and do occur.
Let’s take a look at the specification sheets that trueCABLE publishes to get a closer look at what we are after. Let’s assume you are looking for the proper RJ45 for our bulk unterminated Cat6 Riser Unshielded Ethernet cable:

Cat6 Unshielded Riser Specification Sheet

Cat6 Unshielded Riser Specification Sheet

  • The conductor insulation diameter is 0.96mm
  • The cable jacket OD (overall cable thickness) is 5.90mm
  • The cable is using solid copper conductors and are 23AWG

So, armed with those requirements we would need to choose the trueCABLE Cat6/6A Pass-Through RJ45 connector (if you wish to use pass through).

Cat6/6A Unshielded Pass-Through RJ45 Connector Plug specification sheet

Cat6/6A Unshielded Pass-Through RJ45 Connector Plug specification sheet

We have a match!

Best Practices

  • It is best to keep hand-terminated RJ45 connectors to a minimum
  • Never attempt to create an Ethernet patch cable by using hand crimped RJ45 plugs on both ends when using solid copper Ethernet. Buy factory pre-terminated patch cords for this purpose. If in a pinch, use field termination plugs at both ends when seeking to create a patch cable using solid copper bulk Ethernet cable.
  • Staggered load bar standard (solid nosed) RJ45 plugs are strongly recommended for Cat6A terminations when RJ45 connectors are necessary. Cat6A, when pushed to 500MHz for 10Gb/s operation, generates quite a bit of cross-talk (NEXT) at the connector. When testing with our Fluke DSX-8000, I can produce a 5.0 dB better NEXT parameter when using our Cat6/6A RJ45 standard connector plugs in comparison to our straight-across pass-through variety. This can mean the difference between operating reliably at 10G or being stuck at 1G. The better option is our Cat6A Field Termination Plug when dealing with high speed connections that need a male end.
  • When buying cable and connectors from different vendors, try for the middle! For example, if your Ethernet cable has a stated insulated conductor diameter of 1.00mm, then select a RJ45 plug with an insulated conductor range of 0.95 to 1.05mm. This will give you the best fitment and performance and also allows for tolerance changes from lot to lot (which on Ethernet cable can vary as much as +/- .05mm).
  • Cable strain relief boots are strongly recommended to help stabilize the mechanical (and therefore electrical) connection by helping to prevent cable shift at the rear of the RJ45 connector. The weakest link in the system is always the termination. Strain relief boots take additional strain off of the termination contacts, and help remind you of the cable bend radius.
  • Buy more connectors than you need. It is wise to test terminate (crimp) the connectors onto the cable to make sure you can work with them. In addition, if you make a bad crimp then you can simply use any extras. Even the most experienced installers make a bad crimp from time to time.
  • If you are new to this kind of activity, then practice as much as practical. The more terminations you make, the better you will get.
  • If you do make a bad termination, then the connector is trash and cannot be reused

    Did You Know?

    RJ45 connectors come in four primary types:
    • Standard (solid nose) non-stagger eight across
    • Standard (solid nose) load bar staggered (four high, four low)
    • Pass-through non-stagger eight across
    • Pass-through staggered (four high, four low)

    Staggered style plugs were originally designed to accommodate cable with thicker insulated conductors. If lined up eight across, the conductors would exceed the external size of the RJ45 plug and thus need to be staggered. Technically speaking, there is nothing in the ANSI/TIA 568-2.D specification which dictates RJ45 plugs should be staggered for any particular Category, not even Cat8.

    Strain latch engaged and crimping into cable jacket (left).  Strain latch presser bar cut-out (right).

    Strain latch engaged and crimping into cable jacket (left).  Strain latch presser bar cut-out (right).

    Some connectors lack a strain latch and also skip the rectangular cut-out where the strain latch is found. This rectangular notch is found near the open end of the plug. In order to crimp a connector of this type, a crimp and termination tool that has an adjustable strain latch presser bar such as our All-In-One Crimp and Termination Tool is required. If not adjusted out of the way, the presser bar will destroy the rear of your RJ45 plug. This is often found with large shielded connectors that also have an external ground. The external ground tab serves as the strain relief in this case. The external ground tab must be firmly and properly crimped down in order to avoid electrical connection issues! None of the RJ45 connectors that trueCABLE sells require the strain latch presser bar to be disengaged.

    So, now you know enough to select the correct RJ45 connector for your next Ethernet project. Practice makes perfect, so my sincere advice is to dive right in and start putting on connectors. You will likely make mistakes, but that is the best kind of learning.



     trueCABLE presents the information on our website, including the “Cable Academy” blog and live chat support, as a service to our customers and other visitors to our website subject to our website terms and conditions. While the information on this website is about data networking and electrical issues, it is not professional advice and any reliance on such material is at your own risk.

    Albert Kleyn February 14, 2020

    DON, Yet again an excellent and clearly written article.
    Am most grateful for the down to earth and supurbly written explanations.
    Albert, Rep. Of Ireland.

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