Mountain equipment firelite sleeping bag left zip for ultra light backpacking and alpinism it is difficult to conceive a bag so reliably warm being any lighter perfect for high mountain use during the summer and at lower altitudes in spring and autumn features plasma tm 10d outer shell is incredibly light and exceptionally breathable 469g of 90 10 russian goose down with a minimum fill power of 800 alpine fit with exl system improves loft and maximises thermal efficiency slanted box