glock oem vs aftermarket parts kit

Glock OEM vs Aftermarket Parts Kits (Buyers Guide)

When breaking down the Glock platform into its main components, we identify the frame, slide kit, lower parts kit, and upper parts kit (whether OEM or aftermarket). Each of these high-level categories contains numerous individual pieces, but together, they constitute the core of the Glock.

A quick online search for “Glock parts” yields about 55,900,000 results. The extensive options available for the Glock are unmatched by most firearms on the secondary market.

For new builders, whether assembling a Polymer 80, a Geisler Defence G19x, or adding enhancements to an OEM Gen 5, the initial step often involves chasing shiny objects. At some point, we’ve all indulged in this, myself included.

Building out a cartel-style G19 with all the gold fixings—gold slide locks, pins, slide releases, magazine wells, etc.—can result in a firearm that looks either impressive, cringeworthy, or somewhere in between.

Pause. Let’s step back and ask a more important question: How does the Glock perform?

Many websites claim to offer “upgraded extractors” or “failsafe guide rods,” but how well have these components been tested? Often, we don’t know. What we do know is that OEM Glock parts have undergone rigorous testing with substantial time and budget resources, which aftermarket parts often lack.

Are aftermarket parts bad? Not necessarily, but they do require vetting, testing, and potentially more expenditure for a less superior product. If this is an everyday carry weapon or one you plan to rely on in critical situations, I highly recommend using OEM parts.

Glock Parts Kits (Upper & Lower)

Let’s start by noting what is included in a Glock parts kit. The composition of Glock parts doesn’t differ significantly between OEM and aftermarket, except for a few modifications, such as extended slide releases or varying recoil spring weights.

Glock OEM & Aftermarket Upper Parts Kit

glock upper parts kit

Both Glock OEM and aftermarket upper parts kits generally include the following components:

  • Firing Pin: Strikes the primer to ignite the cartridge.
  • Firing Pin Spacer Sleeve: Guides the firing pin and reduces noise.
  • Firing Pin Spring: Returns the firing pin to its forward position.
  • Firing Pin Spring Cups: Retains the firing pin spring in the slide.
  • Extractor Depressor Plunger: Pushes the extractor down to release the casing.
  • Extractor Depressor Plunger Spring: Provides tension for the depressor plunger.
  • Spring Loaded Bearing: Assists in ejecting spent casings.
  • Firing Pin Safety: Blocks the firing pin unless the trigger is pulled.
  • Firing Pin Safety Spring: Provides pressure to keep the firing pin safety in place.
  • Spacer Sleeve: Maintains the proper position of the firing pin safety.
  • Extractor: Removes spent casings from the chamber.
  • Extractor Spring: Provides tension for the extractor to grip the casing.
  • Slide Cover Plate: Covers the rear of the slide and retains components.
  • Channel Liner: Protects the firing pin channel from debris.

Optional Parts (Often Included with Slide Kit):

  • Rear Sight: Allows for aiming alignment with the front sight.
  • Front Sight: Works with the rear sight for proper aiming.
  • Recoil Spring Assembly: This consists of the recoil spring and guide rod, which absorbs recoil and returns the slide to its forward position.

Glock OEM & Aftermarket Lower Parts Kit

glock lower parts kit

Both Glock OEM and aftermarket lower parts kits typically include the following:

  • Trigger Housing with Ejector: Houses the trigger mechanism and ejector.
  • Trigger with Trigger Bar: Initiates firing when pressed, connected to the trigger bar.
  • Trigger Pin: Holds the trigger in place within the trigger housing.
  • Trigger Spring: Provides resistance and return force for the trigger.
  • Slide Stop Lever: Locks the slide open after the last round is fired.
  • Slide Stop Lever Spring: Provides tension for the slide stop lever.
  • Locking Block: Reinforces the frame and guides the slide.
  • Locking Block Pin: Secures the locking block to the frame.
  • Magazine Catch: Retains and releases the magazine when pressed.
  • Magazine Catch Spring: Provides tension for the magazine catch.
  • Trigger Housing Pin: Secures the trigger housing to the frame.
  • Connector: Transfers energy from the trigger to the firing pin, affecting trigger pull weight.
  • Trigger Safety (Glock “Dingus”): Prevents unintentional firing by blocking trigger movement.

Buying Glock Upper & Lower Parts Kits

Glock offers an extensive aftermarket selection of parts, and there are several places to procure OEM parts kits. However, finding OEM parts can be challenging for two reasons: Glock does not sell OEM lower or upper parts directly, and there is a large number of counterfeit Glock OEM parts sold on marketplaces such as eBay.

Best OEM Glock Parts Kits

#1 Pick
Marine Gun Builder

Marine Gun Builder is a go-to spot for anyone into building custom Glocks. They offer a wide range of Glock OEM parts, including upper parts kits, lower parts kits, and slides, making it easy to find everything you need for your build.

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Ebay OEM Glock Parts

Ebay offers a wide range of OEM Glock parts, but caution is advised due to the prevalence of counterfeit items on the platform. It's essential to verify the authenticity of parts and purchase from reputable sellers to ensure reliability and quality.

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Best Aftermarket Glock Parts Kits

#1 Pick
Husky Armory

Husky Armory offers a variety of aftermarket parts kits for those looking to customize their Glock. Their G19 and G17 lower parts kits are known for being the best budget option on the market.

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JSD Supply

JSD Supply offers a range of Glock parts kits, including both OEM and aftermarket options, tailored for DIY firearm builders. They provide comprehensive kits for Glock-compatible lower and upper parts, emphasizing quality and compatibility to ensure reliable firearm assembly with ease​.

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MDX Arms

MDX Arms offers a comprehensive selection of Glock parts kits, including both OEM and aftermarket options. Their kits cover essential components for Glock builds, such as slide and lower parts, and are designed for various Glock models.

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OEM Glock Parts Reliability and Performance

Using OEM Glock upper and lower parts comes with several benefits, especially for those who value reliability, quality, and compatibility. Here are some key advantages:

glock oem

Quality Assurance

OEM parts are manufactured by Glock, ensuring they meet the company’s stringent quality standards. This results in parts that are reliable, durable, and high quality.


OEM parts are designed to work seamlessly with Glock firearms, eliminating compatibility issues that can arise with aftermarket parts.


Glock’s reputation for reliability is partly due to the quality of its parts. Using OEM components helps maintain this reliability, reducing the likelihood of malfunctions and ensuring consistent performance.

Warranty Compliance

Using OEM parts helps maintain the firearm’s warranty. Aftermarket parts might void the warranty, leaving you without manufacturer support if something goes wrong.

Resale Value

Firearms with OEM parts often retain higher resale value compared to those with aftermarket modifications. Buyers generally prefer original parts due to the associated quality and reliability.


OEM parts undergo rigorous testing to ensure they meet safety standards, which is crucial for firearms where component failure can have serious consequences.

Performance Consistency

Glock OEM parts are designed to work together, providing consistent performance. This is particularly important for upper and lower parts, which need to interact smoothly for optimal operation.

Easy Replacement

If a part needs to be replaced, finding an OEM part is straightforward. Glock offers a wide network of dealers, and parts are readily available, ensuring that you can maintain your firearm without hassle.


In the end, whether you choose OEM or aftermarket parts for your Glock build depends on your priorities. OEM parts offer unmatched reliability, compatibility, and quality, ensuring your firearm performs consistently and safely. They also maintain warranty compliance and resale value. On the other hand, aftermarket parts can provide customization and potential cost savings, but they require careful vetting to avoid issues. Sticking with OEM parts is a wise choice for critical situations or everyday carry.

Happy building, and may your Glock perform flawlessly!

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