Stud Ext Alum 9/16-18 Unf 1.000" Lg W/ Seat. QA1's Aluminum Shock Extensions can give you a little more length if needed for your application. With 1 or 2 inch lengths and 9/16 or 1/2 inch thread sizes, you are sure to find one that will fit your needs. Part #9029-163 for all Circle Track shocks except 70 and 82 Series.