Tomorrow the price will be higher! Fits Inside Factory Coil Spring. Durable, Elastic Polyurethane Construction. Control Air Pressure For Varying Loads & Road Conditions. Usually we offer the best price within 10-15 minutes. If you’re looking for a smoother ride in your coil-sprung truck, the Firestone Coil-Rite Helper Springs are what you need. Coil-Rite Helper Springs are designed to fit inside your existing coil springs to create a variable spring rate. These air helper springs were designed to work in temperatures between -40F & 180F. I have no idea why truck manufacturers thought putting coil springs on the rear axle was a good idea. Luckily these airbags resolved the issue.