Guide rod replacement for Smith's 4-Stone, 3-Stone, and 2-Stone Precision Sharpening Systems. Use this guide rod with the following products: Smith's 4-Stone Diamond Field Precision Sharpening System (item # DFPK) Smith's 3-Stone Diamond Precision Sharpening System (item # DPSKP) Smith's 3-Stone Standard Precision Sharpening System (item # SPSK) Smith's 2-Stone Standard Precision Sharpening System (item # 50169)