[Strong Breaking Strength]: Zipline pulley has a maximum breaking strength of 30 kN (6,700 lbs), suitable for various 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: 13 mm (0.5 in); maximum cable diameter: 12 mm (0.47 in). Compatible with 1/4, 5/16, 3/8, and 1/2 inch cables or ropes. This twin cart is lightweight and durable for outdoor use. [Material]: Zipline pulley features an aluminum and magnesium alloy housing with a stainless steel sheave. The double sheaves ensure smooth rotation and efficient performance. [Efficient Working]: Equipped with two stainless steel discs and sealed stainless steel ball bearings to reduce twisting, enhancing speed and efficiency. Features high-performance bearings for fast operation. This tandem pulley offers improved performance over single pulley systems.