Secures the shifter boot on '05 to '14 Mustangs™ with wide boot opening (1-1/4" diameter) when installing a new aftermarket "ball style" shift knob. Also serves as a jam nut for the shift knob. This is the correct boot retainer for '07 - '09 Shelby Mustangs™ that have a factory installed shifter. Solid billet aluminum with black finish. 12mm x 1.25 thread size. Made in the USA. Please measure your shifter thread size prior to ordering.