The single density
PU sole provides enhanced slip resistance, thanks to the different sized cleats that reflect the natural pressure zones of the foot.
A cushioned shoe, for those with a neutral gait, has a soft midsole made from ethyl vinyl acetate single density
(EVA) recommended for use by males 180 pounds or less and females 150 pounds or less.
The original floppy drive was single-sided, single density
, which was then increased to double-sided, then double-sided, double density, and finally to the high density and double-sided disk we use today as the 1.44-MB floppy.
These are multilayer melt blown webs now available in roll form, as single density
webs have been for years.