Scooter-like traits began to develop in motorcycle designs around the 1900s. In 1894, Hildebrand & Wolfmüller produced the first motorcycle that was available for purchase. Their motorcycle had a step-through frame, with its fuel tank mounted on the down tube, its parallel two-cylinder engine mounted low on the frame, and its cylinders mounted in line with the frame. It was water-cooled and had aradiator built into the top of the rear fender. It became the first mass-produced and publicly-sold powered two-wheel vehicle, and among the first powered mainly by its engine rather than foot pedals. Maximum speed was 40 km/h (25 mph). The rear wheel was driven directly by rods from the pistons in a manner similar to the drive wheels of steam locomotives.