Lesney Matchbox 1-75 Superfast Series
In 1969, Lesney retooled their cars to replace the heavy and fairly wide axles of the original series with thinner axles that would reduce friction. The wheels were also reworked to allow for a much faster toy. Hot Wheels had released cars that were advertised to be much faster than the competition, but they did not patent their design, so Lesney quickly responded with the Superfast Series. The color scheme was reworked as well so that the cars would be brighter, a response to Hot Wheels bright color scheme. The series ran from 1969 until 1983, shortly after Lesney suffered bankruptcy. By 1983, the term 'Superfast' was mostly obsolete because nearly all die-cast car manufacturers had switched to the low friction axles and wheels, so the series was retired.
The above text uses material from the Wikipedia article "Lesney Products" and is licensed under the GNU Free Documentation License.