ID = 1 1/2 OD = 1 3/4 Tube adapters are a basic necessity for every DIY Fabricator. No matter if you are building a four link set up for you new rock crawler or you own heavy duty steering linkage for your trail rig you have to have them. These weld in inserts make it easy to fabricate adjustable linkages. All of our tube inserts are CNC machined.