Gridfinity Breadboard Holder Stackable 1x1x9U.

The model consist out of 2 parts that can be easily glued together. reason for this is to keep maximum strength with minimal filament. Glue the bottom and middle part together. The top part is there in case you want to stack something on top. Just stack it on top of the middle part.
there are 2 different middle parts. The one named middle full is easier to print but uses a bit more filament.

I printed this using a 0.6 mm nozzle but can be easily printed with a 0.4 mm nozzle.
15 % infill.
print the middle part on the side to get the most strength.