Trolleys are what make zip lines so fun.  They turn your backyard into an adventure that makes your heart beat a little faster. The trolleys with built-in handlebars are the most versatile because you can hold on with your hands or attach a harness or seat or both.  The smaller trolleys are less expensive and more compact, you can stow them in your pocket if you need to hike back to the starting launch pad.  All trolleys have a connection point to add your preferred accessories.