Aramid fibres are about 43% lighter than glass fibres (aramid fibre: density ~ 1.44 g/cm³, glass fibre: density ~ 2.55 g/cm³). Nevertheless, they are significantly stiffer than glass fibres and, similar to carbon fibres, almost ten times stiffer than aluminium (based on tensile strength tests). Aramids show excellent dimensional stability with a slightly negative coefficient of thermal expansion. They are largely resistant to chemicals and offer a very good thermal stability over a wide temperature range: even at temperatures in the range of -196 °C (-320 °F), neither embrittlement nor the loss of strength properties occur. Aramid fibres do not melt or burn, but are carbonised at temperatures around 427 °C (800 °F). Because of these properties, aramid fibres are used in components with high impact resistance, heat resistance or chemical resistance.