WEBThe Cisco 4000 Series contains six platforms: the 4451, 4431, 4351, 4331, 4321 and 4221 ISRs. This PDF includes overview, appearance, benefits, specifications and ordering information of Cisco ISR 4000 Series routers. Learn more details: http://nhprice.com/cisco-4000-series-routers-the-king-of-isr.html.