Constructed of BCY Dynaflight 97 material Excalibur’s Matrix Crossbow String produces two distinct advantages. First, it increases speed, which is a key attribute of Matrix Series crossbows. The Matrix 380 Xtra, for example, shoots 380 fps! The second advantage is reduced creep which allows you more time shooting, less time tuning. The Excalibur Matrix string also features a proprietary center serving which will give you increased string life. For Matrix 355 & 380 only.