If you've bought a stripped slide for your Glock, the next thing you need is a slide completion kit. But what's actually in one? And do you need anything else to get your slide running? Here's every part explained.
What Is a Slide Completion Kit?
A slide completion kit (also called an upper parts kit) contains all the small internal components that go inside a Glock slide. These are the parts that make the firing mechanism, extraction system, and safety systems work. Without them, a stripped slide is just a piece of machined steel.
When you buy an assembled slide from 3CR Tactical, all of these parts come pre-installed. But if you're buying a stripped slide — or replacing worn internals — you'll need a completion kit to populate the slide.
Every Part in a Slide Completion Kit
Firing Pin (Striker)
The firing pin is the spring-loaded rod that strikes the primer of the cartridge when you pull the trigger. In a Glock, it's held under spring tension inside the firing pin channel. When the trigger bar releases the firing pin lug, the spring drives the pin forward into the primer.
Firing Pin Spring
This spring keeps the firing pin under tension and returns it to the rearward position after each shot. It's a critical safety component — without it, the firing pin could move forward under inertia alone.
Firing Pin Safety (Plunger)
This is a small spring-loaded plunger that blocks the firing pin channel. It physically prevents the firing pin from moving forward unless the trigger is pulled. When you press the trigger, the trigger bar pushes the plunger up and out of the way, clearing the path for the firing pin. This is one of three passive safeties in the Glock system.
Firing Pin Safety Spring
The small spring that keeps the firing pin safety plunger engaged. It ensures the plunger returns to the blocking position after each shot.
Extractor
The extractor is a claw-shaped piece that grabs the rim of the cartridge case as the round is chambered. After firing, as the slide moves rearward, the extractor holds the spent case against the breech face until the ejector (which is in the frame, not the slide) kicks it out of the ejection port.
Important: Extractors are caliber-specific. A 9mm extractor is different from a .40 S&W extractor. Make sure your kit matches your caliber.
Extractor Depressor Plunger
This spring-loaded plunger sits behind the extractor and provides the tension that keeps the extractor claw engaged with the cartridge rim. Proper tension here is critical for reliable extraction.
Extractor Depressor Plunger Spring
The spring that provides forward pressure on the extractor depressor plunger. This maintains consistent extractor tension.
Spring Cups (2)
Small metal cups that sit at each end of the firing pin spring. They distribute the spring's force evenly against the firing pin and the spring-loaded bearing.
Channel Liner
A small plastic or polymer tube that lines the firing pin channel inside the slide. It reduces friction on the firing pin and keeps debris out of the channel. It's a simple part but important for smooth, consistent striker movement.
Slide Cover Plate (Back Plate)
The flat plate that snaps onto the rear of the slide, holding all the internal components in place. To disassemble the slide internals, you remove this plate first — everything else comes out from the rear.
Recoil Spring Assembly (sometimes included)
Some completion kits include the recoil spring and guide rod. This is the spring that sits under the barrel and returns the slide to battery after each shot. If your kit doesn't include one, you'll need to buy it separately — and make sure it matches your model and generation.
What's NOT in a Slide Completion Kit
A slide completion kit does not include:
- Barrel — purchased separately, matched to your caliber and model
- Sights — front and rear sights are sold separately unless your slide comes with them
- Red dot optic — if your slide has an RMR cut, the optic is a separate purchase
- RMR cover plate — if you're not running an optic, you'll need a cover plate to protect the optic cut
Gen 3 vs Gen 5 Kits — Are They Interchangeable?
No. Gen 3 and Gen 5 slide completion kits are not interchangeable. Key differences include:
- The firing pin safety plunger geometry differs between generations
- The extractor design changed from Gen 3 to Gen 5
- The slide cover plate shape is slightly different
- The recoil spring assembly is a different design (Gen 5 uses a flat wire spring)
Always match your completion kit to your slide's generation. If you're buying a Gen 3 aftermarket slide (which is the vast majority of aftermarket slides), you need a Gen 3 kit.
Do You Need a Completion Kit If You Buy an Assembled Slide?
No. An assembled slide comes with all internals pre-installed — barrel, completion kit parts, sights, and recoil spring assembly. You drop it onto your frame and it's ready to go.
Every assembled slide at 3CR Tactical ships complete with a barrel, all slide internals, tall co-witness sights, and a recoil spring assembly.
Slide Completion Kits at 3CR Tactical
Gen 3 (fits Gen 1–3 slides):
- 3CR Tactical Slide Completion Kit with Recoil Rod for Glock 19/23 — $45
- 3CR Tactical Slide Completion Kit with Recoil Rod for Glock 17/22 — $45
- 3CR Tactical Slide Completion Kit with Recoil Rod for Glock 26 — $49
- 9mm Slide Completion Kit with Recoil Rod for Glock 43/43X — $59
Gen 5:
OEM:
Bottom Line
If you're buying a stripped slide, a completion kit is the fastest way to get all the internals you need in one package. Match it to your generation and caliber, add a barrel and sights, and you have a working slide.
If you'd rather skip the parts-matching entirely, browse our assembled slides — everything comes pre-installed and ready to drop onto your frame.
DISCLAIMER: "GLOCK" is a federally registered trademark of GLOCK, Inc. and is one of many trademarks registered by GLOCK, Inc. and GLOCK Ges.m.b.H. Neither 3CR Tactical nor this site are affiliated in any manner with, or otherwise endorsed by, GLOCK, Inc. or GLOCK Ges.m.b.H. The use of any "GLOCK" trademarks on this page is merely to advertise the sale of pistols, parts, components or accessories that are compatible with GLOCK pistols. For genuine GLOCK, Inc. and GLOCK Ges.m.b.H. products and parts visit www.glock.com.