Sight glass material?

[Boomer]

The MCI one is a sealed threaded, you simply screw it into the bushing.

[stevet903]

Some more ideas:

http://radiatorgroup.com/sightglass.aspx

[eagle19952]

Some more ideas:

http://radiatorgroup.com/sightglass.aspx

good stuff i'm sure..."Sight glass is sold as is with no installation support **"

[jackhanow]

the mci site glass is a good idea. you dont have to make a large hole, just braze the bushing to the tank and drill a quarter inch hole at the top and bottom after you braze the bushing to it.