"Thickness" is the the smallest of three dimensions: length, width, thickness.
Applicable units are those of quantitykind:Length
http://www.merriam-webster.com/dictionary/thickness
http://dbpedia.org/resource/Thickness
"Thickness" is the the smallest of three dimensions: length, width, thickness.
http://www.iso.org/iso/catalogue_detail?csnumber=43012