Description The Time-Sert 4212-125 spark plug thread repair kit is commonly used on Harley Davidson and other motorcycles. The Time-Sert 4212-125 kit includes 6 inserts of which (2) 9mm, (2) 15mm and (2) 17.5mm reach. Additional inserts can be purchased here. This spark plug thread repair kit is for first time thread repair only. Click Here For Instructions Click here: for video instructions Order Washer Seat Inserts Click Here Get Useful Tools, Tap Guides, and More Click Here