This Aluminum T-pipe is designed to have a Type H/RFL BOV (or compatible) attached directly to it. The required mounting hardware should have been included with your BOV (they are not included with this item.)
This T-pipe also has a lip on both ends to firmly hold your couplers in place.
BOV is sold separately.This T-Pipe works perfectly with our Type 11 BOV.
The inner diameter of the BOV port on top is 1 inch. Because of the thickness of the metal on the BOV port, some people say a 1.25 inch coupler works better for them.