Sig P365 Fitment Guide: Slides, Barrels, Recoil Springs, Grips & Small Parts
Posted by Fdez Werx on 27th Oct 2026
This guide expands on our P365 slide and barrel compatibility post. It covers Fdez Werx P365 slides, barrels, recoil spring assemblies, grip modules / magwells / base plates, and common small parts. Use it before you order so barrel length, port style, and RSA all match the slide.
All Fdez Werx P365 parts are drop-in fit.
Because the Sig Sauer P365 Fire Control Unit (FCU) is modular, any Fdez Werx P365 slide will mount on a P365, P365X, P365XL, X-Macro, or Fuse grip module. Grip fit is not the same as a recommended setup: see the grip section for Macro vs XL notes on Fuse slides.
1. Quick Rules
- Ported barrels fit every Fdez Werx slide of the same length: 3.7" fits XL/Macro 3.0, ACCS, and RS; 4.3" fits Fuse 3.0, ACCS, and RS.
- V-port barrels do not fit RS slides. V-port fits 3.0 and ACCS of the same length only.
- 4.3" Fuse threaded or non-ported barrels can be used in shorter slides such as the XL (the barrel extends past the slide). Ported 4.3" barrels cannot be used in shorter slides.
- 4.3" Fuse V-port barrels are coming soon; they will fit Fuse 3.0 and Fuse ACCS slides, but not RS slides.
- Optics: SIG-LOK footprint uses M4 screws; RMSc footprint uses M3. Holosun 407K, 507K, EPS Carry and similar optics can mount on either footprint, but fit best on RMSc.
2. Slide Fitment Matrix
All Fdez Werx slides ship stripped unless you select installed add-ons. Optic cuts are typically RMSc and/or SIG-LOK (listed as SIG-LOC on some pages).
| Fdez Werx Slide | Barrel | RSA | Grip notes | Shop |
|---|---|---|---|---|
| Comp'd Macro / XL 3.0 High Polish 3.0 | 3.7" ported, V-ported, or non-ported XL | XL / Macro RSA (std or tungsten) | XL or Macro grip modules; sits flush with Macro dust cover | Shop |
| Comp'd XL ACCS | All Fdez 3.7" barrels: ported, V-ported, or non-ported (not 3.1") | XL / Macro RSA (std or tungsten) | XL or Macro grip modules | Shop |
| 365RS Comp'd XL 3.7" | 3.7" ported (not V-ported) | XL / Macro RSA (std or tungsten) | XL or Macro grip modules | Shop |
| Fuse 4.3" | 4.3" Chunk Port, 4.3" ported, 4.3" V-ported (coming soon), or 4.3" non-ported | Fuse 4.3" RSA (std or tungsten) | Macro grip recommended (see grip section) | Shop |
| Fuse ACCS 4.3" | 4.3" Chunk Port, 4.3" ported, or 3.7" non-ported (comp'd) | Fuse 4.3" RSA (std or tungsten) | Macro grip recommended | Shop |
| 365RS Fuse 4.3" | 4.3" Chunk Port or 4.3" ported (not V-ported); or 3.7" non-ported (comp'd) | Fuse 4.3" RSA (std or tungsten) | Macro grip recommended | Shop |
3. Barrel Fit / Does Not Fit
| Barrel | Fits | Does not fit | Shop |
|---|---|---|---|
| 3.7" XL Non-LCI Flush & Crown (non-ported) | Fdez XL/Macro slides (3.0, ACCS, RS) | Do not pair a non-ported barrel with a ported window expecting gas venting through the ports | Shop |
| 3.7" XL 3.0 / ACCS Ported | All Fdez XL/Macro slides: 3.0, ACCS, and RS | OEM XL / Macro / XXL / Fuse slides (use the matching Fdez slide window) | Shop |
| 3.7" XL 3.0 V-Ported | Fdez XL/Macro 3.0 and ACCS slides with matching V-port geometry | RS (365RS) slides; XXL slides | Shop |
| 3.1" Non-LCI Flush & Crown / Ported | Standard P365-length setups that call for a 3.1" barrel (see product page) | Do not use in place of a 3.7" XL or 4.3" Fuse barrel unless the slide is designed for 3.1" | Flush & Crown / Ported |
| 4.3" Fuse Ported | All Fdez Fuse slides: 3.0, ACCS, and RS | Shorter XL/Macro slides; V-port-only windows; OEM Fuse slides without matching ports | Shop |
| 4.3" Fuse Chunk Port | All Fdez Fuse slides: RS, 3.0, and ACCS | XL/Macro (3.7") slides | Shop |
| 4.3" Fuse Non-Ported (Flush & Crown) | Fdez Fuse slides; can also be used in shorter slides such as the XL (barrel extends past the slide) | N/A for length — confirm holster clearance when used in a shorter slide | Shop |
| 4.3" Fuse Threaded (with thread protector) | Fdez Fuse slides; can also be used in shorter slides such as the XL (barrel extends past the slide) | N/A for length — confirm suppressor / holster clearance | Shop |
| 4.3" Fuse V-Ported | Fuse 3.0 and ACCS (when available) | RS Fuse; coming soon to the website (no live product page yet) | Coming soon |
| 3.7" Ported (XXL / XXL 2.0 only) — Discontinued soon | Fdez XXL / XXL 2.0 slides only (XXL slides discontinued). XXL slides use only non-ported 3.7" barrels or this soon-to-be-discontinued XXL ported 3.7" barrel. | XL 3.0 / ACCS / RS / Fuse slides | Shop |
Safety: Match port geometry to the slide’s top window. A ported barrel in a non-ported window (or the wrong port pattern) can send gas and debris in unsafe directions.
4. Recoil Spring Assemblies
| RSA | Fits | Shop |
|---|---|---|
| XL / XXL / Macro Adjustable RSA (standard guide rod) | XL/Macro slides (3.0, ACCS, RS) | Shop |
| XL / XXL / Macro Tungsten Adjustable RSA | XL/Macro slides (3.0, ACCS, RS) | Shop |
| Fuse 4.3" Adjustable RSA (standard) | Fuse slides (3.0, ACCS, RS) | Shop |
| Fuse 4.3" Tungsten Adjustable RSA | Fuse slides (3.0, ACCS, RS) | Shop |
| OEM-style P365XL RSA | XL-length setups that call for a factory-style XL RSA | Shop |
| OEM-style P365 RSA | Standard P365-length setups | Shop |
Do not put an XL RSA in a Fuse slide, or a Fuse RSA in an XL/Macro slide. Fdez Werx RSA install uses the stepped spacer (small end in the slide opening, flush); start lighter and work up. See the FAQ for break-in and tuning notes.
5. Grip Modules, Magwells & Base Plates
- XL / Macro slides (3.0, ACCS, RS) fit both XL and Macro grip modules, and sit flush with the Macro dust cover.
- Fuse slides fit Macro grip modules. They physically go on an XL grip, but that is not recommended: the slide overhangs well past the dust cover and the recoil spring assembly is exposed. Use a Macro grip.
- AXG grips are the same as the Macro grip module, just made of aluminum, and have the same overall fitment as the polymer Macro grip. Slide and barrel fitment for AXG matches the Macro.
- Fdez back straps fit the P365 Macro / Carry grip module and work with factory and aftermarket magwells.
| Part | Fits | Shop |
|---|---|---|
| P365 Macro EDC Magwell | P365 Macro / Carry grip modules | Shop |
| 17rd Aluminum Mag Base Plate | P365 Macro 17rd magazines | Shop |
| +3 / 20rd Aluminum Mag Base Plate | P365 Macro magazines (extended) | Shop |
| FDEZ-1 / FDEZ-2 / FDEZ-3 / FDEZ-2R Back Straps | P365 Macro / Carry grip modules | Shop FDEZ-1 |
| Fdez P365 Flat Trigger | All P365 variants (per listing) | Shop |
6. Optic Screws & Small Parts
| Item | Fit / notes | Shop |
|---|---|---|
| RMSc footprint screws | Use M3 (store sells M3 x 0.5 – 10mm in black or stainless) | Black M3 / Stainless M3 |
| SIG-LOK footprint screws | Use M4 (optics ship with standard M4 screws; use the screws supplied with your optic) | — |
| Holosun 407K / 507K / EPS Carry | Can mount on either footprint; fit best on RMSc | — |
| P365 Slide Completion Kit | Factory Sig internals to complete a stripped Fdez slide | Shop |
| Extractor / striker / sear / takedown / mag release kits | OEM-spec P365 / P365XL small parts; see each listing for exact model notes | Browse P365 |
7. Completing a Build
Typical stripped-slide build: Fdez slide + matching barrel + matching RSA + Slide Completion Kit + correct optic screws + (optional) magwell / base plates / back strap. Browse P365 Slides, P365 Barrels, and the shorter slide/barrel matrix.
8. FAQ
Can I put a Fuse slide on an XL grip?
It will physically mount, but it is not recommended. The slide overhangs past the dust cover and the RSA is exposed. Use a Macro grip module.
Does a ported 3.7" barrel fit my 365RS XL slide?
Yes. Regular ported (not V-ported) 3.7" barrels fit RS. V-port does not.
Can I run a 4.3" Fuse barrel in an XL slide?
Threaded or non-ported 4.3" barrels can extend past a shorter slide. Ported 4.3" barrels cannot be used in shorter slides.
Which optic screws do I need?
RMSc = M3. SIG-LOK = M4. Holosun K-series / EPS Carry fit either footprint but fit best on RMSc.
Are Fdez slides sold complete?
No. They ship stripped unless you select installed add-ons (sights, completion kit, barrel, RSA) on the product page.