See the write-up for the AIRE 12" thwart for more details. This seven inch Inflatable Kayak Seat / thwart is somewhat less fancy than the 12" version in the way that the side attachments work (these attachments are shown clearly in the photo above). A lot of people use this smaller thwart for a footrest. We believe this is a better call than using it to support your lumbar area, which it does very poorly.
Note that we also stock a $35 old-style Tomcat inflatable backrest/seat that's almost the same size as this one, though the Tomcat "seat" (which some paddlers also use as a footrest) does not attach to the floor quite as securely as this one or the 12" version. The Tomcat backrest also uses a small twisty-valve for inflation, whereas this 7" AIRE Thwart and it's bigger brother use the same Leafields found on the AIRE kayaks.