MSR IsoPro is a performance-boosting, 80/20 blend of isobutane and propane, with the purest isobutane (5% or less n-butane) of any canister fuel. This clean-burning formulation maintains higher internal pressure at lower temperatures than standard butane/propane mixtures, delivering superior cold weather performance and more consistent output over the life of the canister.A built-in float gauge determines how much fuel is left.This size fits inside the 1.0L Reactor and WindBurner Stove System.Available in store only. MSR IsoPro Gas - 110g