Glock slide completion kits: what is inside and what is not

A stripped Glock slide is a block of steel with holes in it. A slide completion kit is the set of small parts that make it fire: the striker and its spring, the safety plunger that blocks it, the extractor that pulls the case, the liner the striker rides in and the plate that holds it all together. This guide lists what is in a kit, what is usually not, how generation and caliber decide which kit you need, and the order to fit the parts.

What is inside

Striker, or firing pin: the rod that hits the primer. Caliber and generation specific.
Firing pin spring, spring cups and spacer sleeve: the spring that drives the striker, the two half-cups that hold it and the polymer sleeve behind them.
Firing pin safety and spring: the plunger that blocks the striker until the trigger bar lifts it. The drop safety in the slide; its spring stays factory weight.
Extractor: the claw that pulls the fired case. Caliber specific, and LCI or plain on Gen 3 and Gen 4, Gen 5 its own.
Extractor depressor plunger, spring and bearing: the assembly behind the extractor that tensions it; the bearing must match the extractor type.
Firing pin channel liner: the plastic tube pressed into the striker channel.
Slide cover plate: the polymer plate at the rear.

What is usually not

A kit is the slide's internals and nothing more, and the parts left out are the ones that vary by taste and by model. Sights, because the choice is personal and the dovetail takes any Glock sight. The barrel and the recoil spring assembly, which are model specific and sold separately or in a slide and barrel combo. The optic and its screws. A few kits include sights or a recoil assembly and say so; most do not, and a build that assumes they are included stalls on the bench. The combo guide covers the barrel and recoil side.

Generation and caliber

Gen 1 to Gen 4 slides share one set of completion parts in each caliber: the 9mm kit fits a 9mm Gen 3 or Gen 4 slide, the .40 and .357 SIG share a kit with their own extractor, and the 10mm and .45 large frames use their own striker and extractor. Gen 5 slides need a Gen 5 kit: the striker, firing pin safety, extractor and cups all changed. Slimline slides need a slimline kit. Buy the kit for the slide, not the frame; a Gen 3 pattern aftermarket slide takes the Gen 3 kit regardless of what frame it sits on.

Factory versus aftermarket parts

The two parts that decide reliability are the extractor and the firing pin safety, and Glock's own are the safe choice; several American makers cut good ones as well, and a reputable kit maker will say whose. The striker is where the aftermarket adds options: stainless for corrosion, lightweight for lock time on a match gun, extended tip for hard primers. A carry build wants a factory-weight striker spring and a standard striker; a match build can go lighter with testing. The channel liner, cover plate, cups and sleeve are the same from anyone.

Order of assembly

Press the channel liner into the striker channel with a liner tool or a wooden dowel until it seats.
Drop the firing pin safety spring and plunger into their hole from the underside; the plunger's flat faces forward.
Depress the plunger and slide the extractor into its slot from the side, claw forward.
Slide the depressor plunger assembly into its channel behind the extractor, bearing toward the extractor.
Assemble the striker: spring over the striker, compress, fit the two cups against the collar, sleeve over the rear. Wear eye protection.
Slide the striker assembly into the channel from the rear, then press the sleeve and the depressor plunger down and slide the cover plate on from the bottom until it clicks.

Checks

With the slide off the frame, push the striker forward from the rear; the tip must not appear at the breech face until you depress the plunger, and the plunger must spring back flush. Press the extractor; it should pivot against its spring and return. Fit the barrel and recoil assembly, put the slide on the frame, and run the function checks in the build guide before live fire: trigger safety, drop safety, slam test, reset. Then 200 rounds.

Cleaning a new kit

New parts arrive with machining oil and sometimes a little grit. Wipe every part dry before assembly, run a dry patch through the striker channel once the liner is in, and oil only the extractor's pivot and the outside of the striker lightly; the channel itself stays dry. A completion kit assembled dirty gives a gritty pull and light strikes that get blamed on the parts.

Buying the kit

Match the caliber and the generation of the slide, check the list on the page for what is included, and buy sights and a recoil assembly alongside if the kit leaves them out. A kit with a Gen 5 striker will not go into a Gen 3 slide, and a .40 extractor will not run 9mm brass; the listing tells you which you are buying. See the whole build in building a Glock 19, the lower in frame parts kits, and the savings in upgrade bundles. Browse slide completion kits; they ship to your door.

General information, not legal advice. Current as of September 2026. Laws change; check the official source before you act.