What do "M", "L" and "XXL" in the product name mean?

The M, L and XXL in the name of the product is used to determine its width. The "M" is 15-9/16" wide and almost identical in width to the previous generations of Classic and T-LOC Systainers. The "L" is 20" wide and the "XXL" is 31-3/16" wide.