Excalibur Crossbow Matrix String Green. 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 Series crossbows only. Features of Excalibur Crossbow Matrix String: For Matrix Series crossbows only Constructed of BCY Dynaflight 97 material Proprietary center serving which will give you increased string life Increases speed Reduced string creep Package Contents: Excalibur Crossbow Matrix String Constructed of BCY DynaFlight 97 material. Reduces creep and increases speed. Fits the Matrix series crossbows. 31 inches in length.