Extra Comfort
The EVA material that NEOS insoles are made of is a dense foam polymer known as Ethylene Vinyl Acetate and it has an excellent, durable shock absorbing quality. So, EVA is the ideal substance to walk or stand on. Using EVA insoles will help relieve aches and pains from walking and standing for long periods of time on your feet.
Eco-Friendly
The EVA insoles are considered eco-friendly because they don't use chlorine in producing the insoles. This means there is less toxicity released in the land fill when you discard your EVA insoles once they old and worn out.Warmth
EVA insoles add extra warmth and insulation as they act as an extra insulated layer between your foot and the cold outdoor surface you are walking on. If you have non-insulated NEOS, using EVA insoles will extend the length of your usable season by adding warmth to the footbed.Versatility
They can be used if you plan to wear different footwear inside your NEOS to accommodate the size differences. For example, if you buy your NEOS to fit over a pair of boots for the winter, you could use a pair of EVA insoles so that your runners would fit inside your NEOS for during milder weather conditions.
References
http://blog.planetshoes.com/2009/05/eco-friendly-footwear-materials-the-eva-foot-bed/