Supersprings Solo SumoSprings are designed to enhance your vehicles load carrying ability, stabilize sway, and improve overall driver control and comfort. Solo SumoSprings are maintenance free and do not require any airlines or compressors. The air inside Sumosprings is captured in millions of air pockets inside the micro-cellular urethane material. This means that there will be no leaking or rupturing like traditional air bags. Supersprings Solo SumoSprings are a one-piece unit and only mount at one end. Solo Supersprings come in blue, black, and yellow. Blue -40 density captures more air in the micro-cellular bubbles, creating an air spring suitable for light and medium duty applications. Black -47 density balances the amount of urethane and air bubbles suitable for light, medium, and heavy duty applications. Yellow -54 density traps a smaller amount of air in the air spaces creating a strong air spring perfect for medium and heavy duty applications | SuperSprings Solo SumoSprings SSR-407-40