Guide wires are of various types and sizes. Straight tip and curved or J tipped guidewires are the two basic types. Curved J tip reduces the chance of vascular dissection during introduction into the vessel. The thickness of the guidewire depends on the type of application. Guidewires for PTCA balloons are very thin of the order of 0.014 inch while guide wires for catheters are 0.032 – 0.038 inch. Shorter guide wires are used for introducing the sheaths into the arteries and veins. Standard length guide wires are used for introducing catheters into the aorta. Exchange length guide wires have almost double the length of standard guide wires and are needed for catheter exchange from difficult locations.