After looking I realized Pet Gear offers other types besides the booster style seat and wanted you to know this is the seat I've got.
Pet Gear Black Booster Car Seat at PETCO
And, here is some interesting information on sizing with the Snoozer seat.
Pet Products Size Guide - Snoozer Pet Products
When dh gets home later (he drove the SUV today) I'll measure the other seat but am certain it's got to be a large and what I just ordered I know is the medium (and would be crowded with Ruby and Reno). The large is listed as big enough for a 25lb dog and most likely that would work, but might be a bit crowded for two dogs.