Safety First Safe strap + Adjustable Safety Belt + Seat + Reliable Braking System for Maximum Security. Our 60mm swing seats are more sturdy and thicker than other 38 mm swings,which can hold up to 330 lbs. The length is adjustable from 3.6ft to 6.5ft by adjusting buckle, so it will suitabale for kids of different ages and sizes. Our zipline kit with harness has much more safety than the zipline kit with seat. High Quality Steel Cable Trsmima Ziplines for Backyards is designed with your children s safety top of mind .Our 150FT high-altitude zipline is made ultra-strong, galvanized aircraft stainless steel cable,. With durability and weather resistance, Sling Cable comes with zipline tree protect tube to avoid any hurting to your trees.