[Strong Breaking Strength] This zipline pulley has a maximum breaking strength of 30KN (6700LBS), making it suitable for a wide range of outdoor applications such as rescue operations, swing seats, or backyard zipline setups. [Cable Diameter] This tandem speed dual trolley is designed for use with ropes and cables. Maximum rope diameter: 13mm (0.5in). Maximum cable diameter: 12mm (0.47in). Compatible with 1/4, 5/16, 3/8, and 1/2 inch cables or ropes. The twin cart is lightweight and durable for outdoor use. [Material] The zipline pulley features an aluminum and magnesium alloy shell with a stainless steel pulley. The double sheaves ensure smooth rotation and efficient performance. [Efficient Working] Equipped with two stainless steel discs and sealed stainless steel ball bearings to prevent twisting, enhancing speed and efficiency. High-performance bearings support fast operation. This tandem pulley offers improved performance over single pulley systems.