Since I grew up in a country that refused to embrace the metric system, I am more accustom to thinking in terms of inches and not millimeters. So, when designing models I was having a hard time visualizing the thickness of walls in terms of millimeters. To help me I created this little model that shows layer heights for 1 mm thru 10 mm in 1 mm increments. This allows me to not just see but also feel with my fingers how thick layers are.