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OEM replacement aftermarket Diesel Oxidation Catalysts (DOCs) by Redline Emissions Products.

QUALITY. Every DOC goes through an extensive inspection process to verify OEM performance, specifications and fitment. REP DOCs have a 2-year, unlimited mile warranty*

SELECTION. Many aftermarket vendors cover the top movers, we go deeper!  We offer the most extensive parts offering in the emissions systems parts industry.

AVAILABILITY. REP stocks a multi-million dollar inventory spanning warehouses in the US and Canada to offer 1-to-3-day delivery of the parts you need to most locations.

PACKAGING. REP DOCs are packaged in accordion boxes with foam padding to protect the unit in transit and are clearly labeled with all the important part/OEM/crosses information.

TRAINING. Have questions?  We are here to assist with whatever product education, technical, and sales support you may need.

DOCs by Redline Emissions Products


We invite you to watch a video, download our product booklet, or just look around this page. See for yourself how REP DOCs are a value-add to your parts business. Curious to see if we have a particular DOC or look up a part# cross reference, then try our OEM Search tool.

Redline Emissions Products® offers aftermarket DOCs (diesel oxidation catalysts) for Class 3-8 diesel vehicles. Our DOCs are built to meet OEM specs & fit seamlessly with other emission components.

REP DOCs are shipped with the correct, high-quality replacement gaskets free of charge and feature a 2-year unlimited mileage warranty.


One feature that sets REP DOCs apart is the higher level of quality. So, what does that mean?

Our extensive quality assurance process for DOCs involves cleaning and inspecting welds, flanges, etc. We also check each Weld Bung port. Any filters found to be out-of-spec are rejected. The DOC is then weighed and labeled.

REP DOCs are designed to perform to the same flow and performance as the OEM unit ensuring the same results as the OEM unit being replaced.

This provides confidence for resellers & distributors and reduces the chances of downtime because of a product failure due to defects.

 Visual Inspection

Checking Bung Ports

Weighing the DOC

Labeling the DOC


Many aftermarket vendors cover just the top sellers, we go deeper! 

We offer the most extensive parts offering in the emissions systems parts industry.

With over 30 SKUs and growing, REP DOCs offer broad coverage for all the popular manufacturers including Cummins, Detroit Diesel, Dodge Ram, Duramax, Ford, Sprinter, Navistar, Paccar, and Volvo / Mack.

REP DOCs apply to a broad range of LD/MD/HD applications.

Easy to use website with the industry-leading OEM parts cross-search tool to help you find the right filter.

REP DPFs & DOCs in our Warehouse
REP DPFs for most manufacturers/brands


Having a great selection is just one aspect of a healthy parts distribution system. Availability is key.

We have invested in providing strong and speedy availability of our full line of aftermarket of DOCs.

It helps no one if you need to wait a week or more for your part.

REP stocks multiple warehouses in the US and Canada to offer quick coast to coast, delivery of the DOCs you need, when you need them.

If the part is not on the shelf, you cannot sell it! REP maintains a multi-million-dollar inventory of aftertreatment parts to be your go-to supplier.

REP Availability Map

Note: Transit times were based on the information available at the time. Actual transit times vary based on many factors.


We believe durable packaging and proper labeling are essential to serving you and your HD aftertreatment parts customers

All REP DOCs are packaged in sturdy, accordion-style boxes with thick foam to hold the unit securely in the center of the box to prevent damage in transit.

All REP boxes are labeled with the REP part number and serial number. We further include application information: Engine make/ model, as well as OEM, cross-over information to confirm to your customer that they are getting the part they need.

All REP DOC boxes include installation guidelines and warranty registration forms.

All REP DOCs include required gaskets. DOCs with weld bungs include a tube of anti-seize.


Emissions systems are complex; we help take the mystery out of them through training and education! 

We can provide product-specific and aftertreatment systems training for your salespeople. Boost your customer service and profits by having a more knowledgeable and confident parts and sales staff.

REP offers Industry-specific training for your service and parts team. Areas include product-related training (DOCs), diagnostic support, technical support, and best practices for “finding the right part”

REP Training Options
In summary, REP offers high-quality, hand-inspected MD/HD DOCs for a broad range of applications that are available nationwide from multiple warehouses.
Interested in learning more about REP DOCs, or becoming a REP distributor?
Click the links below.
REP DOCs provide quality, selection, availability, packaging and training

Ready to start selling DOCs?


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Any questions about REP DOCs?

CALL 1-888-295-4670

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