6" wall cap -- equivalent in linear feet?

Hi,
I am installing a bathroom exhaust fan. The duct run consists of a section of 6" round aluminum flex duct, 6" round metal duct, and terminates with a 6" wall cap like the one pictured at the following URL:
http://www.serv-air.com/b641.html
What I am trying to find out, is the approximate equivalent of this style of wall cap, in feet. For instance, the tech specs of my particular fan says it can accomdate runs of 50 feet of 6" ducting. I found the conversion for the flex duct (it was 2x), but have not seen anything for the wall cap.
Does anybody know the conversion for a 6" wall cap, so I can use it in my calculation and make sure I my duct system will perform adequately?
Thanks,
Scott
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Scott, Call Toll Free 1.888.833.4510 for the answer to your question.
Jabs

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.