QA1 3-1/2in ID Tapered Spring - 8in Length x 500lbs/in - Chrome PlatedQA1's Mustang II Pro Coil Kits feature polished and chrome plated springs. They have a 3. 5" upper I. D. and 2. 5" lower I. D., these springs have an 8" free length and are offered in four rates. Made with the highest quality materials, QA1 springs are strong, consistent and have a long life. All QA1 springs come with a lifetime guarantee to remain within 2% of their original free height and rate, so you know you're getting quality springs with QA1.