This is IP2-J+ Fisher-Koch surfaces with 50% infilled volume (t=0).There is set of two complimentary volumes made by division of a single solid cube with IP2-J+ surface. They are not identical like those made with Diamond, Gyroid or some other surfaces, that give two similar or identical (t=0) volumes mirrored by axonometric(?) plane.

This is a part of Fisher-Koch surface crappy mesh catalogue.