There is provided an air spring for supporting a load, the air spring comprises a chamber for holding a pressurized gas in use, a load-bearing surface arranged to transmit a force from a load in use to the pressurized gas held in the chamber. Importantly, in order to lower the spring rate, the chamber contains a mass of adsorptive material. There is also provided a use of an adsorptive material for the purpose of lowering the spring rate of an air spring, including a gas strut and a pneumatic wheel. There is also provided a method of designing an air spring using an adsorptive material to lower the spring rate.