<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by San-Franciscan:
The "SR" designator is used on A320's that are overwater equipped, with life vests at each passenger and crew seat, infant life vests, survival kits, and a transmitter.</font>
The US Shuttle A320s are so equipped and are designated "EOW" (Extended Over Water). I have never seen the "SR" designation on Airbii otherwise.