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. Three Sizes: Sold in 4, 8 and 16 oz. canisters to meet the demands of any stove or trip. The 4 oz. canister is sized to fit inside the 1.0L WindBurnerA(R) and ReactorA(R) Stove Systems. Improved Performance: 80/20 blend of isobutane and propane delivers superior performance throughout the life of the canister and in colder temperatures. Clean-Burning: Zero-maintenance combustion. Fuel Gauge: Built-in float gauge determines how much fuel is left (4 oz. and 8 oz. canisters). Recyclable: Consult your local recycling center for regulations. Due to shipping costs we only sell these in store. Specs 16 oz / 450g 3.9 oz / 110g 8 oz / 227g Width (Standard) 4.4 in 3.5 in 4.3 in Weight (Standard) 1 lbs 7 oz 7.4 oz 13.1 oz Length (Standard) 4.4 in 3.5 in 4.3 in Height (Standard) 6.0 in 2.7 in 3.7 in Country of Origin Made in Korea Made in Korea Made in Korea