Sig Sauer P365 FCU Frame | Custom Works | 8900165

The Sig Sauer P365 Custom Works Fire Control Unit (FCU) is a stripped FCU/frame intended for builders and gunsmiths working on the micro-compact P365 platform. This listing is for the FCU only; it does not include slide, barrel, magazine, or other components. The unit is ATF-classified as a frame and is designed to accept Sig P365 parts and assemblies.

Common applications: everyday-carry (EDC) customization and gunsmithing/custom builds to tailor a P365 to specific carry preferences or ergonomic goals.

Product Specifications

• The manufacturer is listed as Sigd Sauer.
• The model is Fire Control Unit from the Custom Works series.
• The unit fits Sig P365 parts and modules.
• The ATF classification is Frame.
• The ATF model is P365.
• The manufacturer’s part number is 8900165.
• The UPC is 798681626007.
• The product type is listed as Striker Fired.
• The subcategory is Fire Control Unit.
• The trigger style is described as a Flat (flat blade) trigger.
• The listed safety is No Thumb Safety.
• The color is listed as Black.
• The series is Custom Works Fire Control Unit.
• An additional feature listed is a Skeletonized Flat Blade.

Note: finish and caliber/compatibility information appears inconsistently in the source data (see notes). Some materials reference titanium nitride components while attribute data lists black/black nitride finishes; this listing presents confirmed attributes and flags areas for verification in the notes below.

Designed for experienced builders and licensed transfers, this Custom Works FCU provides the serialized basis to personalize a P365 platform without including non-FCU components. It’s a straightforward option for anyone conducting a build or replacing an FCU on a Sig P365-compatible frame.