Around 1903 Rex produced motorcycles with engines above and driving, the front wheel. (the Werner engine position). The engines were Rex’s own, and included singles and V twins. In 1904 there was a 372 cc model which had the silencer cast with the cylinder in one piece. In 1905 the side valve Rex model was rated at 3.25 hp. In 1907 they introduced the Rex Lighweight with a new frame design, the engine was 76mm bore by 80mm stroke (362cc), with automatic inlet valve, and direct belt drive. At the 1908 Stanley Show both 3.5HP single and 5HP twin motorcycles were on show (both with automatic inlet valves), the 5HP with 2-speed gear. For the 1909 show they introduced a 2-stroke with the same bore and stroke as their single, and a pair of 'Speed King' motorcycles, versions of their single and V-twins fitted with rigid frame, unsprung forks, and direct belt drive.