A4 Wagyu is slightly less marbled than A5, however it is still crazily-marbled.
In Japan, highly trained professional graders rate all beef, the best of which earns and A4 or A5 status. For example, to official quality as "Kobe Beef", Wagyu from Hyogo prefecture must achieve an A4 or an A5 rating.
While A4 is still very marbled, you may enjoy more beef flavor and be able to eat more of it in one sitting than a comparable cut that was rated A5. Rest assured, A4 is not only extremely marbled, it is packed with the distinctive umami flavor and lower melting point fat compounds that contribute to the melts-in-your-mouth sensation for which Japanese Wagyu is famous.
To learn more about A4 Wagyu please click here