MSR 40z fuel Cannister

MSR's IsoPro canister holds 110 g of an 80/20 isobutane-propane blend behind a standard Lindal EN417 valve, the threading used by the large majority of upright and remote canister stoves on the market — MSR's own PocketRocket and WindBurner included, along with any other EN417-compatible burner. The 80/20 ratio matters more than it looks: propane has a lower boiling point than isobutane, so a higher propane share keeps the canister's internal pressure — and therefore flame output — more consistent as temperatures drop, compared with blends that lean harder on butane or isobutane alone. That said, canister gas of any blend loses performance as ambient temperature approaches and drops below freezing, since even propane eventually stops vaporizing efficiently in a container that isn't warmed or inverted. With a caloric value of 46.7 kJ/g, it's a standard clean-burning hydrocarbon fuel rather than anything unusual. For 3-season backpacking and thru-hiking where boil times and simplicity matter more than extreme cold performance, it's a straightforward, widely compatible choice; for genuine winter trips, a liquid-fuel stove remains the more reliable option.