The string that comes with the bow is of 450+ material. This is a high performance string much like fast flight but with less noise. It is a very strong string being 150# per strand as opposed to a Dacron string which is 55# per strand. The 6 or 8 (depending on the bows weight) strand may look weak and flimsy but it is a 900 to 1200# string, the equivalent to an 18 strand Dacron. You may use any other type string you wish on your Shrew but the 450+ is what I like and recommend. If you use any other high performance string such as fast flight or other HP string material , the strings loops MUST be padded or doubled. If they are not and you experience any damage to your bow because the string loops are not padded, your warranty will be void.