@VS228 

You can find Deco hardware specs at the following link: What are the differences between different models of Deco? There, it says that Deco E4 is capable of 867Mbps at 5GHz.

Still, are you sure you ask the right question? Usually people are interested in real life performance of an equipment, not theoretical maximums under unrealistic conditions. For E4 specifically, depending how you plan to deploy it, its maximum actual speed it can provide to wireless device connected to it could be as low as 100Mbps.

@Alexandre. 

That speed of 867Mbps is for 5GHz 802.11ac. I'm asking about 5GHz 802.11n. I. e. the client device supports 5GHz, but only 802.11n and not 802.11ac. 

@Alexandre. 

BTW, the 100Mbps speed could be because you are using the E4 as the main deco connected by Lan cable to your router. The E4's ethernet ports support only 100Mbps. That's why I am using the M4 as the main deco and the E4 as the satellites.