Holsters are firearm accessories, and toptenpick.com does not carry affiliate links to firearm-related gear — this guide covers how to choose a concealed carry holster for a Glock 21 without recommending specific purchasable products.
Why the Glock 21 changes the equation
The Glock 21 is a full-size, single-stack-width but wide-grip .45 ACP pistol. It is noticeably larger and heavier than a compact 9mm, which matters more for holster choice than it does for smaller guns: a holster that comfortably conceals a subcompact will often print or dig in when it’s sized for a full-size .45. Fit, ride height, and cant matter more here than brand name.
Material: Kydex, leather, and hybrid
- Kydex (or other rigid polymer) holds its shape regardless of how many times the gun is drawn and reholstered, retains the trigger guard consistently, and is easy to clean. It’s the most common choice for a duty-size .45 because it doesn’t collapse under the gun’s extra weight the way soft leather can over time.
- Leather molds to the body over time and tends to feel less “blocky” against skin, but a full leather holster needs to be built specifically for the Glock 21’s frame, not a generic “large frame” catch-all, or retention and reholstering will be inconsistent.
- Hybrid (leather backing, Kydex shell) tries to combine leather’s comfort against the body with Kydex’s consistent retention at the trigger guard, and is a common middle ground for a gun this size.
Carry position and cant
Inside-the-waistband (IWB) carry conceals a full-size .45 more easily than outside-the-waistband (OWB), but the Glock 21’s grip length and thickness make IWB carry bulkier than it would be for a compact gun — appendix carry in particular gets uncomfortable fast with a taller grip digging into the hip crease when sitting. OWB carry under a covering garment is a common alternative for exactly this reason, trading some concealment for comfort with a larger gun. Whichever position you choose, look for an adjustable cant (the angle of the grip) so the holster can be tuned to your body type rather than forcing one angle.
Retention level
Retention is rated in levels: Level I relies on friction fit alone, Level II adds a manual retention device (commonly a thumb-break strap or button the drawing hand releases), and Level III adds a second mechanism. For concealed civilian carry, Level I (a properly fitted friction-retention Kydex or hybrid holster) is standard and sufficient as long as the holster is molded specifically for the Glock 21 — a loose, generic “fits most Glocks” holster is a real safety risk with a heavier gun, since the extra weight can work a loose holster open during normal movement.
Sweat, comfort, and belt support
A .45-caliber full-size pistol is heavy enough that belt choice matters as much as the holster itself. A stiff, properly sized gun belt (not a standard dress belt) keeps the holster riding level rather than tipping outward, which is the single biggest factor in all-day comfort with a gun this size. Sweat guards — a lip of material between the holster and the body at the top of the slide — are worth prioritizing for a gun carried IWB against skin for long periods.
Buying checklist
- Confirm the holster is molded specifically for the Glock 21 (not a generic “full-size Glock” or “Glock 20/21” catch-all unless the manufacturer explicitly confirms trigger-guard retention on both).
- Decide IWB vs. OWB based on your wardrobe and body type before choosing a specific model — this narrows the field faster than comparing materials.
- Check for an adjustable cant and ride height, since a fixed-angle holster that doesn’t match your body will undermine an otherwise good holster.
- Pair it with a stiff gun belt rated for the extra weight of a full-size .45 — a flimsy belt undermines even a well-fitted holster.
- Where required, check state and local laws on concealed carry before purchasing or carrying.