Arisaka’s new 300 Series Light Body offers a more streamlined alternative to the original light body that is included with the light. They reduced the bulk of the mounting interface to only what is necessary to work with aftermarket light mounts which tend to hold the light closer to the rail. This clears out space around the light, providing clearance for items like your front sight. This is especially important when the light will be used on an offset light mount that holds the light very close to the rail.
The availability of this body also opens up the possibility of building your own light from components including those from Malkoff Devices.