ID = 1 OD Tube adapters are a basic necessity for every DIY Fabricator. This tube insert differs from our standard insert because it has a larger O.D. (1 1/2") at the area to be welded, it is the perfect insert to use if you are using 1/4" wall or thicker tubing. It also has the added benefit of a machined hex making linkage adjustments a much simpler task.