Glock slimline magazines: 43, 43X, 48 and 15-round options
Slimline magazines are simple until you buy the wrong one, and then they are the reason the pistol does not run. The 42, the 43, and the 43X and 48 each use a different magazine, the factory magazines have several extension options, and the aftermarket makes 15-round steel magazines for the 43X and 48 that fit flush and change the pistol. This guide lists what fits what, what the extensions do, where the 15-round magazines can and cannot ship, and how to look after them.
Which magazine fits which pistol
- Glock 42: its own .380 magazine, 6 rounds. Fits nothing else.
- Glock 43: its own 9mm single-stack magazine, 6 rounds. Does not fit the 43X or 48.
- Glock 43X and 48: the same 10-round magazine, a stack-and-a-half design in a polymer body. Interchangeable between the two pistols; does not fit the 43.
Standard-frame Glock magazines, the 17 and 19 magazines, do not fit any slimline pistol.
Factory magazines and floorplates
The 43 ships with a flat floorplate and a floorplate with a finger extension; the extension adds no rounds but gives the little finger a place. The 42 is the same. The 43X and 48 ship with a flat 10-round magazine that fills the grip. Factory magazines are polymer over a steel liner with an orange follower on current production, and they are the reference for reliability: a pistol that runs with factory magazines and not with an aftermarket one has a magazine problem, not a pistol problem.
Aftermarket extensions
For the 43, extensions replace the floorplate and add one or two rounds with a longer spring; +1 and +2 kits from the well-known makers are reliable when the spring in the kit is used. For the 43X and 48, +2 and +3 extensions on the factory 10-round body exist, though they undo the flush grip that made the pistol worth carrying. Any extension is a change to the magazine, and it should be tested through a couple of hundred rounds before it is carried.
The 15-round steel magazines
Several makers sell a 15-round steel-bodied magazine for the 43X and 48 that fits flush in the factory grip, since a steel body is thinner than the polymer factory magazine and holds a wider stack. They turn a 10-round pistol into a 15-round one at the same size, and they are the reason many people choose a 43X over a 19. They are not factory parts: early versions had feed problems, current versions from the established makers are reliable, and any of them should be tested in your pistol before you trust it. They do not fit the 43.
Telling them apart
The 42 magazine is marked .380 on the body and is the shortest. The 43 magazine is marked 9x19 and is a true single stack, one round wide from top to bottom. The 43X and 48 magazine is wider at the bottom than the top, marked 9x19 with the 10-round capacity, and the 15-round steel magazines carry their maker's name rather than Glock's. A magazine that will not seat is the wrong magazine; do not force it.
The follower and the slide stop
The follower's rear tab is what lifts the slide stop on the last round. A worn follower, a dirty magazine or an aftermarket floorplate that lets the spring sit crooked all cause the slide to fail to lock back, which is the most common slimline magazine complaint and rarely the pistol's fault.
State limits
Several states cap handgun magazines at 10 rounds, and a few at 15. The 15-round slimline magazines only ship to states where they are legal; our checkout checks the shipping address before payment, and the rule for your state is on your city page. The factory 6- and 10-round magazines ship anywhere.
Loading and testing
New magazines are stiff; a loader helps with the last two rounds of a 10 or 15. Load every magazine to capacity and shoot it through the pistol at least twice: a magazine that fails to lock the slide back on empty, that drops rounds low into the feed ramp, or that does not drop free is retired or fixed before it is carried. Number your magazines with a paint pen so a failing one can be identified.
Care
Take the floorplate off every few months, wipe the inside of the body, the spring and the follower dry, and reassemble without oil; oil holds lint and swells followers. Carry magazines pick up pocket lint and sweat, so they get wiped more often than range magazines. Springs in a loaded magazine do not wear from being loaded; they wear from cycling. A spring that has softened enough to cause failures is replaced, not stretched.
How many to own
Three for a carry pistol: one in the gun, one spare on the belt or in a pocket, one at home in rotation. More for the range so a session does not turn into a loading session. Keep the carry magazines as factory or a proven 15-rounder and let the range magazines take the abuse.
Carrying a spare
A spare slimline magazine is thin enough for a pocket magazine carrier or a small belt pouch; a 43 magazine disappears into a front pocket. Carry it with the bullets pointing the way your reload hand expects, and practice the reload with dummy rounds until the spare comes out the same way every time. A reload on a small pistol is rarely needed and, when it is, needed quickly.
See which pistol the magazines belong to in the slimline comparison, and the .380 magazine in the Glock 42 guide. Browse 43 and 43X magazines, 48 magazines and magazine carriers; they ship to your door where legal.
General information, not legal advice. Current as of September 2026. Laws change; check the official source before you act.
