This unit replaces the magazine base plate on the SIG P365 (10 rd magazines). This extension does not alter the capacity of the magazine. It adds approximately 5/8" additional gripping surface (1/4" longer than factory extension) as well as enhanced ergonomics. The enhanced griping surface also incorporates a texture which closely matches the frame of the firearm. Model: Sig P365 Finish: Textured Material: Polymer Color: Black