They're some of the largest felids ever, bigger than any extant tiger or lion. I'm pretty sure only Smilodon populator, Panthera fossilis and maybe one of the machairodonts were larger.
IIRC they lived alongside Smilodon fatalis and the short faced bears Arctodus, who were humongous.
Eh, wait, really? I thought it was the other way round? Because tigers are solitary and such.