Motorbikes with piggyback-style shock absorbers sometimes have an internal floating piston (IFP) that separates oil & nitrogen - but much more commonly - a rubber bladder reservoir that holds the gas separately. This heavy duty little balloon is less prone to leaking than the seals of separating pistons, so most OEM rear dampers use them in the piggy back chamber - learn more about shock layouts.

Bladders have end caps in a massive variety of shapes & sizes that all feature air ports so you can regas the shock after a suspension rebuild - some models feature a rubber bung that gets pierced by a regassing needle - while others have easy to refill schrader (tyre) valves. See our regassing tools to get the right style.