Stainless Steel Adapter: [ 1/2" OD, 3/8"-16 MALE x 6mm-1 MALE ]

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Price : $17.70

The 1/2" diameter adapters are typically used DIY pole spear builds who have bought Aluminum tube for their home build.

3/8"-16 Cut type Thread Tap requires a 5/16" hole. If your tubing has a .092" wall you will not need to drill the aluminum tube. [ good axial alignment in taping is critical for straight connections] A form tap uses a .3480" hole (drill size S).