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Fill power is a measurement used to quantify the ability of down to resist compression, known as its loft. The higher the fill power, the more space the down occupies and the more effective it is as an insulator. Higher fill power down is hard to source and therefore expensive, it does however offer significant weight savings for gram-counting alpinists.
In the outdoor industry fill powers tend to start at around 650 and currently go up to 850 (900 does exist but is rare and mostly needs to be 'handplucked' from live birds). The down's origin is also sometimes given, most 'European' down comes from Hungary and the Ukraine and tends to be better quality that Chinese sourced down. The species may also be given but is not strictly speaking informative. The best goose down will outperform the best duck down, but good duck down will outperform poor goose down.
In addition to the fill power figure, there is sometimes a percentage quoted, eg '85% down' or '85/15 down'. This refers to the ratio of pure down to small feathers used. Higher feather percentages tend to be found on less technical products where down is padded out with feathers which cost less and offer more rigidity to compensate for the lower loft, however almost all products contain some feathers to increase the durability of the down.
In the past a number of different competing systems were used to measure fill power. Today almost all outdoor manufacturers use the International Down and Feather Bureau's testing method (sometimes known as the US method). This involves pre-conditioning the down being tested with steam, which gives the best consistency for test results. It is then placed in a cylinder and stirred to maximise its loft, before its volume is measured in cubic inches after being compressed by an ounce weight to give the fill power.
YKK is a Japanese group of manufacturing companies and is the world's largest zipper manufacturer with a reputation for reliable and durable build quality in their zips. It was founded in 1934 by Mr Yoshida and known as Yoshida Kogyo Kabushikikaisha.
Today YKK produces zippers for everything from handbags to wetsuits as well as many other fasteners. They are at the forefront of innovation in fastener design and will generally last longer than similar non-branded designs.
The Rab Neutrino 600 is an incredibly lightweight down sleeping bag, filled with top quality 800 fill power Hydrophobic goose down. It's perfect for summer use, lightweight backpacking, mountain marathons, cycle touring or anytime when saving weight is paramount.
The Neutrino bags have a mummy taper shape that maximises warmth for minimum weight. The bags are hand-filled in Derbyshire by our experienced fillers - some of whom have been with Rab for 20 years - what they don't know about down isn't worth knowing! Pertex Quantum inside and out keeps the shell weight to a bare minimimum.
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