Because the Sig Sauer P365 Fire Control Unit (FCU) is completely modular, any Fdez Werx P365 slide will mount onto any P365, P365X, P365XL, X-Macro, or Fuse grip module. However, matching the right barrel length (3.1", 3.7", or 4.3"), porting style, and recoil spring assembly (RSA) to your specific …