Welcome…to RJ45s.com

The RJ45 Connectivity Experts and Sentinel Connector Systems largest stocking distributor of Made in USA RJ45 modular plugs. Sentinel provides the finest quality and offers the broadest line of RJ45s in the industry. Currently, they manufacture over 100,000,000 plugs and over 38,000,000 strain relief boots a year in their York PA. facility. Since their inception in 1997, Sentinel has shipped over 2,000,000,000 RJ45 plugs.

More about Sentinel.....Bob Brennan, Founder and CEO actually helped invent the RJ45 connector system back in the 70's as part of the Design Team for Western Electric (Bell Labs). He was also formerly in charge of R&D for the Missile Command Center at Redstone Arsenal. We thank him for his service.

RJ45s.com is also proud to distribute Sentinel's built to order UL 3992 Certified Patch Cords with product lead times of 3-7 days ARO. Sentinel's patch cords can be found in Data Centers around the World in Amazon, Google, Microsoft, Netflix, LinkedIn and a host of other well-known facilities.

Our goal is to inform, educate, increase awareness, and explain some PROBLEM AREAS associated with the RJ45 interface.....the WEAKEST LINK in the Network. By doing so, customers will hopefully make better product selections and get the desired results. Please take a few minutes to navigate our site, and we hope you find this information helpful.

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The RJ45 is a Highly Engineered Interconnection System

Beware of substandard, non-compliant, and counterfeit RJ45's coming in from the far East.

Know the standards - Know the specs - Insist on compliance - Know your suppliers


Just Say NO to: 


Somewhere along the line, either through COST PRESSURES, OUTSOURCING, MATERIAL SELECTION, PRODUCT DESIGN, or a host of other reasons, some RJ45 modular connector manufacturers have strayed from the specifications as set forth by the Standards Bodies (such as ACTA, ASTM, EIA, FCC, IEC, IEEE, ISO, TIA and UL). As a result, there is a growing problem in the field relating to POROSITY, OXIDATION, CORROSION, CONDUCTIVITY, CONTACT RESISTANCE, INTERMITTENCIES AND LOSS OF SIGNAL that have become more pervasive recently.


Industry's Best Kept Secret

"Moving at the Speed of Right"



Why Not Go To The Best In The First Place?

Sentinel Connector Systems is the premier "MADE IN USA" manufacturer of RJ-45 Plugs and Jacks. Bob Brennan, Founder, and President of Sentinel Connector (former Founder/President of Stewart Connector), has been involved with RJ45s since its inception. He was part of the team that built the first RJ45 back in the 1970s, consulting with Hardesty and Gustin, who worked at Western Electric creating the FCC Part 68 Specification (superseded by ANSI/TIA-1096-A). Bob and the Sentinel East Team have over 135 foreign and domestic patents relating to the RJ45 Interconnect. Significant Patents include the MagJack, a Proprietary Gold Plating Process called Spot Plating, and a Composite Carbon/Graphite Fiber Conductive Load Bar.

The Sentinel Connector Systems Advantage

THE BOOK OF RJ (Robert J Brennan) Representing over 40 years of handwritten notes about the why's, dos, and don’ts of manufacturing RJ45 Interconnection Systems.

We do everything for a reason. All products meet/exceed the following standards:

ANSI/TIA 568 - ANSI/TIA 1096-A (Formerly FCC Part 68)
CENELEC EN 50173 - IEC 60603-7 - ISO-8877 - ISO/IEC 11801 - UL1863

Sentinel's plugs and jacks are built by industry standards & specifications as set forth by governing bodies such as ACTA, ASTM, FCC, IEC, IEEE, ISO, TIA, and UL. Sentinel is also a Member of the Communications Cable and Connectivity Association, adhering to the Association's strict Code Of Ethics regarding compliance.



  • Sentinel manufactures its plastic components on Battenfeld and Cincinnati molding presses with tightly controlled tolerances and a meticulous Quality Control Program to ensure Standards Compliant Parts.
  • Connectors are assembled with equipment both purchased and designed/manufactured in-house. Unparalleled Quality Procedures and Maintenance Programs ensure that the products are assembled with consistency and reliability, plus the Equipment runs 24/7, LIGHTS OUT.
  • The Quality Department utilizes equipment to test the gold thickness and mechanical properties of all the connectors manufactured.
  • The Engineering Department uses state-of-the-art CAD equipment and has a fully equipped Tool Room to support Manufacturing and New Product Development.


How We Build THINGS – 1

The basis metal for the contacts is Phosphor Bronze. We use a precise percentage along with a very tightly controlled min-max granular MICROSTRUCTURE to provide the best stiffness, spring qualities, and corrosion & wear resistance. The base metal is electro-polished (versus wire-brushed), creating an extremely smooth "BURR FREE" contact surface.

It is then plated with 100 micro inches of pure Nickel (min plugs, 50 micro min jacks), providing a sacrificial metal surface/barrier to PROHIBIT DIFFUSION and OBTAIN THE DESIRED POROSITY CHARACTERISTICS. Then, 50 micro inches (minimum) of pure 24 CARAT (hard) GOLD adhering to MIL-G-45204C, TYPE II, GRADE A specifications and Knoop Hardness requirements. During each plating operation, proper surface activation and cleansing procedures are meticulously followed to ensure against any possible surface contamination and potential GALVANIC REACTIONS (reference MIL-STD-889).


How We Build THINGS – 2

By incorporating the strict design guidelines above, Sentinel Plugs and Jacks will have a MINIMUM 1,000 CYCLE LIFE (insertions/de-insertions) before any degradation of surface contact areas and a 2,000 MINIMUM CYCLE LIFE WHEN USING SENTINEL PLUG/JACK COMBINATIONS.

The bottom line - we do not cut corners and use the best practices. We meet and exceed all standards, we provide the highest quality in the marketplace, and best yet, we are easy to work with, and our products are made in the United States of America.


Helping Companies Meet the Buy American Act

The Buy American Act ("BAA", originally 41 U.S.C. §§ 10a–10d, now 41 U.S.C. §§ 8301–8305) requires Federal agencies to procure domestic materials and products. The latest revision raises the required amount of domestic content from 55% to 60% by 2022, from 60% to 65% by 2024 and from 65% to 75% by 2029.