【Compatible】STIHL series 017, 018, 021, 023, 025, MS170, MS180, MS210, MS230, MS250. Keep your chainsaw running like new. 【Package includes】1 x sprocket, 1 x clutch, 1 x sprocket bearing, 1 x worm gear, 1 x washer, 1 x E-clip, 1 x spark plug. Installation and replacement are quick and easy. 【Perfect fit】Each replacement part fits perfectly with the original part. High-quality sprocket kits allow you to easily repair your chainsaw and restore it to peak performance. OEM Part Numbers: 3/8 LP Pitch Spur Gears: #1123 640 2003 & 1123 640 2073. Clutch Assembly Replacement: #1123 160 2001. Worm Gear Replacement: #1123 640 7102.