Made in France, Petzl’s Tandem Speed works well as the main trolley for an advanced backyard zipline system. Like the C.A.M.P. Wing, the Speed accepts cables up to 15/16 inches in diameter and has a maximum speed of 45 miles per hour. But instead of using a locking mechanism, the Speed is a simpler device, allowing removal from the zipline only after you unclip your carabiner. It's also lighter, at just 9.5 ounces.