You'll get both the forward and rear trailing arm bushing in one box, and it'll save you a little bit of cash when you get them together. Not a bad deal overall really.
Here's a bit of the details.
-Bushing material is a nice and stiff 95A medical grade urethane
-Bushings are graphite impregated for ease of maintenance
-Crush tubes are stainless steel and milled from solid stock.
-Impreza - 2007 and earlier
-Forester - 2008 and earlier
-Legacy - 1999 and earlier