Common Mast Model: A masts, K masts (open-front masts), derricks, masts and bootstrap masts. Jianxin Petroleum owns strong ... mats.Product Features,Common Mast Model: A masts, K masts (open-front masts), derricks, masts and bootstrap masts.A-mast: its leg ... of the drawworks.K-mast its leg section is "K" open face type. The beam legs adopt laminated truss structure. Each ...