All of the bowstrings are in syntheticfibres. Different strings exist and their performance always depends on the percentage of elasticity. The lower their level of elasticity, the more the string with release the energy of the limbs. To keep your string as long as possible you must absolutely "unbrace" your bow after a shooting session to avoid it drawing length along the tension of the limbs and maintain it with wax to protect it against bad weather (damp and heat). This is very simple...