Ordered an Autometer boost gauge but???

I recently ordered an Autometer boost gauge and plan on hooking both the stock gauge and the new one up. Does anyone know what size T-fitting I will need to make this work? Thanks in advance.
-pete

You will need to t-into the stock boost gauge line. It is very small ~3mm I want to say. I ordered some compression fittings from mcmaster.com and a t as well. Take a caliper to your hose to see what you need.

Or you can use heat shrink to go over the factory hose and seal it up.