Glock 20 / 21 Build Planner: Parts, Fit and Prices
Large-frame Glock in 10mm (G20) or .45 ACP (G21). Same size, caliber-specific frame, slide, barrel and mags. 57 parts from 16 brands, each checked for fit against the rest of your build, with prices compared across retailers.
Open the Glock 20 / 21 BuilderStart from a Complete Build
Three Glock 20 / 21 builds where every part already fits, from $571.30. Open one in the builder and swap anything you like.
What's in the Budget Glock 20 / 21
- Frame: Lone Wolf TWF Large Frame, Textured (stripped) $74.95
- Trigger & Frame Parts: Glock OEM Lower Parts Kit, G20/G21 $94.99
- Slide: Glock G20 Gen3 Slide (OEM, stripped) $199.99
- Slide Parts Kit: Lone Wolf Upper Parts Kit, G20/G21 $59.99
- Barrel: Lone Wolf LWD G20 Barrel, 10mm $109.95
- Recoil Spring Assembly: Glock G20/G21 Gen3 Recoil Spring Assembly (OEM) $10.95
- Sights: Glock OEM Polymer Sights $9.99
- Magazine: ETS G20 15-Round Magazine $10.49
What's in the Best Value Glock 20 / 21
- Frame: Glock G20SF/G21SF Gen3 Short Frame (OEM, stripped) $184.99
- Trigger & Frame Parts: Overwatch Precision TAC Trigger, Glock Large Frame $135.00
- Slide: Brownells RMR Cut Slide for Glock 20 Gen3 $219.99
- Slide Parts Kit: Glock OEM Slide Parts Kit, G20/G21 $74.99
- Barrel: Lone Wolf AlphaWolf G20 Barrel, 10mm $134.95
- Recoil Spring Assembly: ISMI G20/G21 Gen3 Stainless Guide Rod & Spring $39.99
- Sights: Trijicon Bright & Tough Suppressor Night Sights, Glock Large Frame $121.52
- Optic: Holosun HS507C X2 $299.99
- Magazine: Glock G20 15-Round Magazine (OEM) $24.99
What's in the Premium Glock 20 / 21
- Frame: Glock G20/G21 Gen4 Frame (OEM, stripped) $189.99
- Trigger & Frame Parts: Overwatch Precision TAC Trigger, Glock Large Frame $135.00
- Slide: Glock G20 Gen4 MOS Slide (OEM, stripped) $279.99
- Slide Parts Kit: Glock OEM Slide Parts Kit, G20/G21 $74.99
- Barrel: Lone Wolf AlphaWolf G20 Barrel, Threaded 9/16x24 $149.95
- Recoil Spring Assembly: Glock G20/G21 Gen4 Recoil Spring Assembly (OEM) $22.95
- Sights: Trijicon Bright & Tough Suppressor Night Sights, Glock Large Frame $121.52
- Optic: Trijicon RMR Type 2, 3.25 MOA $439.99
- Muzzle Device: Lone Wolf Thread Protector, 9/16x24 $14.99
- Magazine: Glock G20 15-Round Magazine (OEM) $24.99
Glock 20 / 21 Parts and Prices
Every Glock 20 / 21 part we list, cheapest first, with the lowest price we found (prices last checked Oct 5, 2026). The builder checks how each one fits with the rest of your parts.
Frame
4 options, $74.95 to $189.99. Serialized. G20 and G21 frames are the same, so the slide sets the caliber.
| Lone Wolf TWF Large Frame, Textured (stripped) Budget PickGen3/4 compatible · No finger grooves · G20/G21 | $74.95 at Brownells (sample price) |
|---|---|
| Glock G20/G21 Gen3 Frame (OEM, stripped)Gen3 · Finger grooves · Fits 10mm and .45 slides | $179.99 at GlockStore (sample price) |
| Glock G20SF/G21SF Gen3 Short Frame (OEM, stripped) Best ValueGen3 · Short frame · Smaller back strap | $184.99 at GlockStore (sample price) |
| Glock G20/G21 Gen4 Frame (OEM, stripped) Premium PickGen4 · Backstraps · Dual-spring channel | $189.99 at GlockStore (sample price) |
Trigger & Frame Parts
3 options, $94.99 to $144.99. Large-frame trigger parts fit both the G20 and G21.
| Glock OEM Lower Parts Kit, G20/G21 Budget PickLarge frame · Stock trigger · ~5.5 lb | $94.99 at GlockStore (sample price) |
|---|---|
| Overwatch Precision TAC Trigger, Glock Large Frame Best ValueLarge frame · Flat face · Uses OEM trigger bar | $135.00 at Brownells (sample price) |
| CMC Triggers Drop-In Trigger, Glock Gen3 10mm/.45 Premium PickGen3 large frame · Flat face · Self-contained housing · ~3.5 lb | $144.99 at Primary Arms (sample price) |
Slide
8 options, $199.99 to $449.99. Its breech face is cut for one caliber. Match it to the frame.
| Glock G20 Gen3 Slide (OEM, stripped) Budget Pick10mm · Gen3 · No optic cut | $199.99 at GlockStore (sample price) |
|---|---|
| Glock G21 Gen3 Slide (OEM, stripped).45 ACP · Gen3 · No optic cut | $199.99 at GlockStore (sample price) |
| Glock G20 Gen4 Slide (OEM, stripped)10mm · Gen4 · No optic cut · Dual-spring recoil | $209.99 at GlockStore (sample price) |
| Glock G21 Gen4 Slide (OEM, stripped).45 ACP · Gen4 · No optic cut · Dual-spring recoil | $209.99 at GlockStore (sample price) |
| Brownells RMR Cut Slide for Glock 20 Gen3 Best Value10mm · Gen3 and 20SF · RMR footprint · 17-4 stainless | $219.99 at Brownells (sample price) |
| Glock G20 Gen4 MOS Slide (OEM, stripped) Premium Pick10mm · Gen4 · MOS plate system | $279.99 at GlockStore (sample price) |
| Glock G21 Gen4 MOS Slide (OEM, stripped).45 ACP · Gen4 · MOS plate system | $279.99 at GlockStore (sample price) |
| Zaffiri Precision ZPS.2 RMR Cut Slide, Glock 20 Gen310mm · Gen3 · RMR footprint | $449.99 at OpticsPlanet (sample price) |
Slide Parts Kit
2 options, $59.99 to $74.99. Firing pin, extractor, safety plunger, backplate.
| Lone Wolf Upper Parts Kit, G20/G21 Budget PickLarge frame · Gen3/4 | $59.99 at Brownells (sample price) |
|---|---|
| Glock OEM Slide Parts Kit, G20/G21 Best ValueLarge frame · Gen3/4 | $74.99 at GlockStore (sample price) |
Barrel
9 options, $109.95 to $184.95. Must match the slide's caliber. A 10mm slide can also take a .40 conversion barrel.
| Lone Wolf LWD G20 Barrel, 10mm Budget Pick10mm · 4.61" · Conventional rifling | $109.95 at Brownells (sample price) |
|---|---|
| Lone Wolf LWD G21 Barrel, Threaded .578x28.45 ACP · Threaded .578x28 | $124.95 at Brownells (sample price) |
| Lone Wolf AlphaWolf G20 Barrel, 10mm Best Value10mm · 4.61" · Conventional rifling | $134.95 at Brownells (sample price) |
| Lone Wolf AlphaWolf G20 10mm to .40 S&W Conversion BarrelFires .40 S&W · Fits a 10mm slide · 4.61" | $134.95 at Brownells (sample price) |
| Lone Wolf AlphaWolf G21 Barrel, .45 ACP.45 ACP · 4.61" · Conventional rifling | $134.95 at Brownells (sample price) |
| Lone Wolf AlphaWolf G20 Barrel, Threaded 9/16x2410mm · Threaded 9/16x24 | $149.95 at Brownells (sample price) |
| Lone Wolf AlphaWolf G21 Barrel, Threaded .578x28 Premium Pick.45 ACP · Threaded .578x28 | $149.95 at Brownells (sample price) |
| Glock G20 Barrel (OEM)10mm · 4.61" · Polygonal rifling | $184.95 at GlockStore (sample price) |
| Glock G21 Barrel (OEM).45 ACP · 4.61" · Polygonal rifling | $184.95 at GlockStore (sample price) |
Recoil Spring Assembly
3 options, $10.95 to $39.99. Goes with the slide: Gen3 single spring or Gen4 dual spring.
| Glock G20/G21 Gen3 Recoil Spring Assembly (OEM) Budget PickSingle spring · Gen3 slides | $10.95 at GlockStore (sample price) |
|---|---|
| Glock G20/G21 Gen4 Recoil Spring Assembly (OEM) Premium PickDual spring · Gen4 slides | $22.95 at GlockStore (sample price) |
| ISMI G20/G21 Gen3 Stainless Guide Rod & Spring Best ValueSingle spring · Gen3 slides · Stainless rod | $39.99 at Brownells (sample price) |
Sights
3 options, $9.99 to $192.00. Large-frame Glock sights. Suppressor height co-witnesses with a dot.
| Glock OEM Polymer Sights Budget PickStandard height · U-notch rear | $9.99 at GlockStore (sample price) |
|---|---|
| Trijicon Bright & Tough Suppressor Night Sights, Glock Large Frame Best ValueSuppressor height · Tritium | $121.52 at OpticsPlanet (sample price) |
| Trijicon HD XR Night Sights, Glock Large FrameStandard height · Tritium · Bright front | $192.00 at OpticsPlanet (sample price) |
Optic
5 options, $249.99 to $539.99. Footprint must match the slide cut.
| Holosun HS407C X2RMR footprint · 2 MOA dot · Solar | $249.99 at Primary Arms (sample price) |
|---|---|
| Holosun HS507C X2 Best ValueRMR footprint · Multi-reticle · Solar | $299.99 at Primary Arms (sample price) |
| Trijicon RMR Type 2, 3.25 MOA Premium PickRMR footprint · Duty-grade | $439.99 at OpticsPlanet (sample price) |
| Aimpoint Acro P-2Acro footprint · Enclosed emitter | $509.99 at OpticsPlanet (sample price) |
| Trijicon SRO 2.5 MOARMR footprint · Large window | $539.99 at OpticsPlanet (sample price) |
Muzzle Device
2 options, $14.99. Threaded barrels: 9/16x24 on 10mm, .578x28 on .45 ACP.
Magazine
8 options, $10.49 to $25.99. Match the slide's caliber: G20 mags for 10mm (and .40 conversions), G21 mags for .45 ACP.
| ETS G20 15-Round Magazine Budget Pick10mm · 15 rd · Flush · Translucent | $10.49 at Primary Arms (sample price) |
|---|---|
| ETS G21 13-Round Magazine.45 ACP · 13 rd · Flush · Translucent | $10.99 at Primary Arms (sample price) |
| ETS G21 18-Round Magazine.45 ACP · 18 rd · Extended | $12.49 at Primary Arms (sample price) |
| ETS G20 20-Round Magazine10mm · 20 rd · Extended | $12.99 at Primary Arms (sample price) |
| Glock G20 10-Round Magazine (OEM)10mm · 10 rd · Flush | $21.99 at Primary Arms (sample price) |
| Glock G21 10-Round Magazine (OEM).45 ACP · 10 rd · Flush | $22.99 at Primary Arms (sample price) |
| Glock G20 15-Round Magazine (OEM) Best Value10mm · 15 rd · Flush | $24.99 at Primary Arms (sample price) |
| Glock G21 13-Round Magazine (OEM) Premium Pick.45 ACP · 13 rd · Flush | $25.99 at Primary Arms (sample price) |
Weapon Light
2 options, $134.99 to $379.00. Must fit the frame's accessory rail.
| Streamlight TLR-7A500 lm · Glock and 1913 rail keys | $134.99 at Primary Arms (sample price) |
|---|---|
| SureFire X300U-A1,000 lm · Universal and Picatinny mounts | $379.00 at Brownells (sample price) |
Holster
6 options, $64.99 to $74.99. Molded for one pistol size, with or without a light.
| Vedder LightTuck IWB, Glock 20Kydex IWB · Optic cut · Open bottom | $64.99 at Brownells (sample price) |
|---|---|
| Vedder LightTuck IWB, Glock 21Kydex IWB · Optic cut · Open bottom | $64.99 at Brownells (sample price) |
| Vedder LightTuck IWB, Glock 20 + TLR-7AKydex IWB · Carries TLR-7A · Optic cut · Open bottom | $74.99 at Brownells (sample price) |
| Vedder LightTuck IWB, Glock 20 + X300Kydex IWB · Carries X300 · Optic cut · Open bottom | $74.99 at Brownells (sample price) |
| Vedder LightTuck IWB, Glock 21 + TLR-7AKydex IWB · Carries TLR-7A · Optic cut · Open bottom | $74.99 at Brownells (sample price) |
| Vedder LightTuck IWB, Glock 21 + X300Kydex IWB · Carries X300 · Optic cut · Open bottom | $74.99 at Brownells (sample price) |
Case
2 options, $54.97 to $109.95. Any pistol case fits; check length if you run a light or comp.
| Savior Equipment Specialist Double Pistol Case, 14"Soft · Two pistols · Mag pouches | $54.97 at Brownells (sample price) |
|---|---|
| Pelican 1170 Protector CaseHard · Watertight · Lockable | $109.95 at OpticsPlanet (sample price) |