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.

Oeko-Tex (the International Association for Research and Testing in the Field of Textile Ecology) is an organisation based in Switzerland which has produced a number of standards to ensure confidence in textiles for manufacturers and consumers. All testing for the standards is conducted by a network of 15 independent labs across the world.

There are currently three levels of certification. Oeko-Tex Standard 100 covers the use of harmful substances in textiles, Oeko-Tex Standard 1000 covers damaging production facilities and Oeko-Tex Standard 100+ is the ultimate level of certification requiring that a product meets both of the other standards.

Quantum GL is the most advanced fabric Pertex have ever made and is a natural evolution of their award-winning Quantum fabric. Precisely woven using incredibly fine 10 denier or less yarns, this family of fabrics are nanolight at less than 25g/m², a full 20% lighter than the original Quantum.

Despite its minimal weight, it is soft, completely windproof and cannot be punctured by down. It also has the smallest packing volume of any Pertex fabric.

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.