Polar fleece (microfleece or simply "fleece") is made from polyethylene terephthalate (PET) an alternative to wool, first was made in 1979 by Malden Mills (now by Polartec LLC),can be made from recycled plastic bottles.

Polar fleece is very good to use like an insulation layer. Fleeces is used in coats, jackets, hats, glovers, vests, mittens and scarves for its thermoinsulation and softness. Polar fleece are made with different thickness like: micro, 100, 200 and 300 (the thickest and least flexible).

Advantages:

• Doesn't Shrink - or unravel when laundered
• Light Weight - have like 320 - 380 g per yard, so is considered medium weight.
• Stretches - in one direction when pulled or tugged on.
• Water Resistant - can retain only 1% of his weight in water
• No Pill Varieties - doesn't have unattractive little balls
• Easy Working With - very easy to work with this fabric
• One Sided or Two - you can purchase with one or two sides

Disadvantages:

• Very flammable - if not  treated with a flame retardant
• Not windproof - the regular polar fleece
• Do not absorb moisture - sometimes is considered an advantage
• Generate static electricity - and attracts dust, pet hair and lint
• Very easy to damage at high temperature - when washing, ironing tumble drying