Stainless Steel Exhaust Springs With Swivel Hook, 57MM, 2Pk. Available In 13 Sizes To Fit Almost All Exhaust System Applications. From 38MM To 100MM, These Premium, Tempered 302 Stainless Steel Exhaust Springs Feature A Swivel Hook For Easier Installation And Endurance. We Recommend Using Our Spring Pull Tool P/N 395-3812. For Proper Measurement And Fitment Follow These Helpful Hints: 1) Exhaust Springs Should Be Measured Off The Vehichle. Always Wear Eye Protection When Removing And Installing Springs. 2) The Length Measurement Should Be Made From Inside Hook To Inside Hook. 3) For Correct Fit, Exhaust Springs Should Not Be Extended More Than 20% Of Free Length.