Gridfinity Holder Bahco Measuring Angle (45° and 90°) Combination Square | Big and Small

The design for the big 305 square is stackable and has a full height of the gridfinity base (6). The small organizer is not deep enough by a few millimeters, so it is not stackable. Both designs contain some additional storage, e.g., a pen.  

The angle is quite cheap and mostly suitable for wood working projects. You can find them on amazon in both sizes.