The type of stent used depends on where it needs to be placed. Coronary and carotid artery stents often have a base made of wire mesh and they are used to open up the arteries to improve the flow of blood to the heart muscle or to the brain. Some coronary artery stents are drug-eluting types which has a layer of medicine that coats the stent and is released overtime to help stop the artery from narrowing. Stents made of polyester fabric with a metal mesh backbone are often used in the aorta to treat aneurysms. These aortic stents are also called stent grafts. Stents that are used to open up the airways are often constructed of silicone or metal, and in some cases they may be a hybrid type made of metal along with another material.