Glock frame parts kits: every part in the lower

A serialized Glock frame arrives as an empty polymer shell with steel rails, and a frame parts kit, sometimes called a lower parts kit, is everything that goes into it: the trigger group, the locking block, the slide stop, the slide lock, the magazine catch and the pins. This guide lists the contents, explains what each part does, sorts the kits by frame type and generation, and gives the installation order.

What is in the kit

Trigger with trigger bar: the shoe and the steel bar whose cruciform holds the striker and whose ramp lifts the firing pin safety.
Trigger mechanism housing with ejector: the block that carries the connector, the cruciform shelf and the caliber-specific ejector; 336 or 30274 for 9mm through Gen 4.
Connector: minus, dot or plus; kits usually ship the dot or the minus.
Trigger spring: the coil that assists the pull.
Locking block: the steel block the barrel lug cams against; three-pin or two-pin.
Slide stop lever and spring: locks the slide back on an empty magazine.
Slide lock and spring: the takedown lever; leaf spring on Gen 3 pattern.
Magazine catch and spring: small on Gen 3, reversible on Gen 4 kits.
Trigger pin, locking block pin and trigger housing pin.

Two-pin and three-pin

The pin count is the first thing to match, because the locking block and the pins in the kit are cut for one or the other. Gen 3 pattern frames, factory and aftermarket, have three pins above the trigger and take the three-pin locking block and the locking block pin. Gen 1 and Gen 5 frames have two pins and their own blocks; a Gen 5 frame needs a Gen 5 kit throughout, since the trigger bar, housing, slide stop and slide lock spring all differ. Almost every build frame sold today is three-pin Gen 3 pattern, and almost every frame parts kit is made for it. Check the frame maker's page and the kit page for the same words.

Caliber

The housing is the caliber-specific part because the ejector is pressed into it: a 9mm kit has the 9mm ejector housing, a .40 kit the .40 housing, a 10mm or .45 kit the large-frame housing with a wider trigger bar. The rest of the kit is shared across the standard-frame calibers. Buy the kit for the caliber of the barrel you will fit.

Factory versus aftermarket

Frame parts are where factory and aftermarket are closest, because there is little to improve: the locking block, ejector housing, slide lock and pins are best cut to the drawing and the factory's are. Kits from established makers use factory-spec parts and often factory parts outright. The places a kit can add value are a flat-faced trigger and a minus connector, and an extended slide stop or magazine catch for shooters who want them. A kit with a set-screw trigger must be adjusted so the firing pin safety is not lifted at rest; the build guide's checks catch it.

What to add

A frame parts kit completes the lower and nothing else. For a build you still need a slide and barrel, a slide completion kit, a recoil spring assembly, sights and magazines; a Gen 4 pattern frame also needs its backstraps and the longer housing pin if you fit one. The build guide lists all of it in order.

Installation order

Magazine catch spring into its channel in the grip, then the catch pressed in against it.
Slide lock spring into its slot, then the slide lock slid in over it; confirm it snaps up.
Hook the trigger spring between the trigger bar and the housing post, set the cruciform in the housing slot, and lower the housing with bar attached into the frame so it seats fully.
Locking block into its seat ahead of the trigger.
Slide stop lever with its spring tucked under the trigger pin channel; push the trigger pin through from right to left while wiggling the lever until it clicks into the pin's groove.
Locking block pin through the upper hole.
Trigger housing pin through the rear of the grip.

Pin fit and frame wear

Pins should go in with firm thumb pressure or a light push from the punch and should not fall out; a pin that drops through an aftermarket frame's hole means the hole is oversized, and the frame maker should hear about it before you shoot. The three pins are the only fasteners in the lower and they take the recoil load through the locking block, so a loose pin is not cosmetic. Stainless and titanium pin sets are the same diameter as factory and change nothing but the look.

Checks on the lower alone

Before the slide goes on: the trigger moves when the blade is pressed and not from the side; the trigger spring returns the bar forward; the slide lock snaps up; the magazine catch holds an empty magazine and releases it. With the slide on: the full checks in the build guide, then 200 rounds.

Buying the kit

Match the frame pattern, three-pin Gen 3 or two-pin Gen 5, and the caliber of the barrel. Check the connector and trigger shoe the kit ships with; a minus connector and a flat shoe save a second purchase. Pair it with the upper from the combo guide and the completion kit guide, and see the savings in upgrade bundles. Browse frame parts 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.