GPL-31XT. Basically this is a group 31 AGM with a slightly increased capacity (125 at the 20 hr rating). Most group 31s come in at between 95 and 105 so while the increase might seem small, for those in RVs and such with space restrictions, that difference can mean quite a lot. Being a 12 volt battery, it is a drop in affair for quite a few of those applications.
Lifeline states their batteries can take some very high charge rates so that is something to consider especially in small systems but where the charger is capable of high rates.
The solar version is the PVX-1290T. http://www.sunxtender.com/solarbattery.php?id=36