Par Aide® Dura-Flex™ 5630-25 Yellow with Black Letters Drop Zone Sign. Our exclusive Dura-Flex™ Signs survive years of punishment from wayward carts and whatever else your course can dish out. Thick, flexible and maintenance-free material with raised 3D lettering and a molded-in continuous spike. They're held firmly in place by robust U-shaped stainless steel spikes, molded into the sign bodies.