Which Async Module we need for 4531 router

[md.irfan.khans]

Hello All, 

Which Async Module we need for 4531 router  , Also do you have anyone Router comparison between 2951 and 4000 series 

[Philip D'Ath]

https://www.cisco.com/c/en/us/products/routers/4000-series-integrated-services-routers-isr/relevant-interfaces-and-modules.html#async-wan-interface

[md.irfan.khans]

Thanks Philip , for your reply . How can i get the Part Number ? 

[Philip D'Ath · Accepted solution]

The part numbers are in the link I gave you. For example, the 16 port async module has the part number NIM-16A.