Jack, It would be nice if model size were one of the standard named parameters you could plug into a relation and be done. However, you can pick Info/Model Size which will display the size in the infomation area. You can then mouse select, cut and paste that value right into the Parameter dialog box after selecting "+" to create a new parameter. Most of this could be automated with a mapkey. Just a reminder that the size displayed is the so-called "diagonal of the bounding box". It's not totally clear to me that that's what you are looking for. Also, if you are able to create an Analysis that yields height, width and depth (not trivial in the general case), then the size is simply the square root of the sum of their squares. You can grab that result easily with a relation. David