The J-I was a Solid-fuel rocket expendable launch vehicle developed by the National Space Development Agency of Japan and the Institute of Space and Astronautical Science. In an attempt to reduce development costs, it used the solid rocket booster from the H-II as the first stage, and the upper stages of the M-3SII. It flew only once, in 1996, in a partial configuration, to launch the demonstrator Hyflex. The vehicle never flew in the final orbital capability configuration, which should have launched the OICETS satellite (which was finally launched on Dnepr).
On the Hyflex mission a load of 1,054 kg was launched 1,300 km downrage.