# Have there been any square 4U (2x2) cubesats?

How much did each MarCO 6U cubesat weigh? suggests that the density of a MarCO 6U cubesat might be as low as 0.75 g/cm^3 whereas I think they are usually about twice that.

That led me to speculate that their insides might have been able to fit into a 4U configuration but since the reflectarray antenna needed to be roughly 6U-sized it didn't make sense to try to squeeze it into 4U.

Question: Have there been any square 4U (2x2) cubesats?

Are there any reasons why the 2x2 configuration might be undesirable?