It was in 5.0 mustang & superfords September 2002 page 33.
It reads.
SUPERIOR DESIGN,,,, Boosts engine performance and effiency by sampling the exhaust more than 60 times per sec to maintain a constans air-fuel ratio.
ALUMINUM OXIDE TRAP LAYER,, Keeps siliconne and lead outside the ceramic element through Denso's exclusive design, preventing damage from oxygen sensor destroyers like racing gs or fuel and lead additives.
POROUS [PTFE] FILTER,,, Increases performance by allowing atmospheric oxygen to enter the sensor without permitting water or engine contaminants to steep into the casing.
Call or visit our web site for a dealer near you.
www.DensoAftermarket.com
That's all it says, I am assuming that all there O2's are that way.
Hope some of that helped.