Standard Conventional Progressive Spring - 20" Length | 5" OD | 225lbs/inchSwift conventional springs are mainly utilized in motorsports ranging anywhere from dirt to pavement where we've engineered for corner specific with our HS5. TW proprietary material, providing the optimal spring design to maximize your vehicle potential amplifying every advantage. The Progressive Springs were developed to eliminate the need for spring rubbers to help keep consistency on the right rear of a Dirt Late Model. A true progressive rate!