Flue Material?

Hey Guys-

What type of flue material is this and does it have any clearance requirements from combustibles? Thanks.

Kenny

Transite

http://www.inspectapedia.com/sickhouse/asbestoslook7.htm#bannertop

Thanks Chris, I figured it had been discussed in the forum somewhere but wasn’t sure what to search under. Is that type of pipe then treated as a single-walled vent and therefore should have a 6" clearance from combustibles?